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Linux kernel CVE-2026-98432: IPv4 TCP use-after-free (CVSS 9.8), RHEL patches released, Ubuntu fixes in -proposed, Anthropic AI-written remote root exploit

6 fonte(s) · 10 atualização(ões) · publicado 28/10/2026 05:15 · coletado há 15 horas

Matéria consolidada. Reúne 6 matérias que o Tifon tinha publicado separadamente sobre a mesma história. A IA reescreveu o relatório com o que as 6 fontes trouxeram em 04/11/2026 00:10; os links antigos trazem para cá.

Fontes: thehackernews.com ×3 ↗ gbhackers.com ×3 ↗ fortiguard.fortinet.com ↗ aikido.dev ↗ bleepingcomputer.com ↗ darkreading.com ↗

CVE-2026-98432 is a race-condition use-after-free in the Linux kernel IPv4 TCP connection setup path, present since kernel 4.4. The kernel CVE team scores it 9.8 CVSS; Red Hat initially scored it 5.9 Moderate but has since raised its own rating to 9.8 Critical (thehackernews.com). Anthropic disclosed on October 27 that an unreleased Claude model wrote an exploit giving unauthenticated remote root on Linux servers with a multipath TCP (MPTCP) listener, bypassing KASLR (thehackernews.com, bleepingcomputer.com). This was the most serious of five lab-built proof-of-concept chains (Chrome, Safari, Android, Windows, Linux) that Anthropic's Frontier Red Team disclosed the same day; all were reported to vendors beforehand and none were seen in real attacks (thehackernews.com, gbhackers.com, darkreading.com). The fix landed upstream in early-to-mid October, credited to Anthropic researcher Xinyang Ge; sources differ on the exact date (see Conflicting Reports). Debian, Oracle Linux, SUSE and Amazon Linux have shipped fixed kernels. Red Hat released fixed kernels for RHEL 8, 9 and 10 on November 1 via RHSA-2026:93414, RHSA-2026:93412 and RHSA-2026:93413, requiring a reboot (thehackernews.com). Ubuntu published fixes for 22.04 LTS and newer in the -proposed pocket, not yet in default updates, with no release date given as of November 2 (gbhackers.com, thehackernews.com). Ubuntu says Anthropic's exploit is still unreleased and no other exploit is known (gbhackers.com). No in-the-wild exploitation has been reported, and the flaw was not in CISA's KEV catalog as of October 30 (thehackernews.com). Fortinet PSIRT published advisory FG-IR-26-188 on November 2, but the source does not say which Fortinet products are affected (fortiguard.fortinet.com).

Entenda a falha

A vulnerabilidade

CVE-2026-98432 is a race-condition use-after-free in the Linux kernel IPv4 TCP connection setup code, present since kernel 4.4. An unauthenticated remote attacker who can reach a listening TCP port can send SYNs with IPv4 Record Route or Timestamp options and retransmit them to win the race, causing a memory leak, corruption or a crash. The kernel CVE team scores it 9.8; Red Hat raised its own score from 5.9 to 9.8, SUSE gives 8.1 and Amazon 7.0. Anthropic reports remote root on servers with an MPTCP listener, but Ubuntu says the flaw is not MPTCP-specific. Fixed in 5.10.272, 5.15.223, 6.1.190, 6.6.159, 6.12.113, 6.18.56, 7.2.10 and 7.3. RHEL 8/9/10 were fixed on November 1; Ubuntu fixes are still in -proposed. IPv6 is not affected by the main race. CVE-2026-33096 is a separate Windows HTTP.sys denial of service (7.5), mentioned only in passing.

Como funciona

During a TCP handshake the server keeps the IP options from the client's SYN with the pending request. When the connection completes, tcp_v4_syn_recv_sock() hands those options to the new child socket without copying them. If the client retransmits its SYN, another CPU can handle it for the same request and build a SYNACK through tcp_check_req(), tcp_v4_send_synack() and inet_csk_route_req(), reading the options under rcu_read_lock() only. ip_build_and_send_pkt() and ip_options_build() then read the options length twice. If the child socket is destroyed meanwhile and its options freed, the SYNACK builder reads freed memory. A similar race exists when request sockets are migrated and the old and cloned requests share the same options.

Por que é vulnerável

Since commit 079096f103fa, request sockets are processed without the listener lock, so nothing prevents the child socket from being freed while a SYNACK is still being built. TCP child sockets lack SOCK_RCU_FREE, and inet_sock_destruct() frees inet_opt with a plain kfree() even though readers rely on RCU. In migration (net.ipv4.tcp_migrate_req=1 or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE program), the clone made by inet_reqsk_clone() shares ireq_opt and tcp_v4_reqsk_destructor() also uses a plain kfree(). Other paths that replace inet_opt already use kfree_rcu(). The fix uses kfree_rcu() in both destructors, so memory is reclaimed only after current RCU readers finish.

Onde está

Linux kernel IPv4 TCP: tcp_v4_syn_recv_sock(), tcp_check_req(), tcp_v4_send_synack(), ip_options_build(), reqsk_timer_handler(), inet_sock_destruct() and tcp_v4_reqsk_destructor(); the fix is titled "ipv4: free inet_opt and ireq_opt after an RCU grace period" (Fortinet PSIRT FG-IR-26-188), and the overlap became possible after commit 079096f103fa.

Como foi descoberta

The kernel fix credits Anthropic researcher Xinyang Ge with reporting the bug; the articles do not say how it was found. Sources differ on the upstream fix date: one report says October 5 (ten days before the CVE was published on October 15), another says October 15. The kernel CVE team added the 9.8 score on October 24. On October 27 Anthropic's Frontier Red Team said an unreleased Claude model, after initial prompting, wrote a remote root exploit for servers with an MPTCP listener, one of five lab chains reported to vendors beforehand. CloudLinux's kernel team says it could not reproduce that claim. Red Hat shipped fixes on November 1 and raised its score; Fortinet published FG-IR-26-188 on November 2. No vendor, CERT or the kernel team reports exploitation in the wild, and it was not in CISA's KEV as of October 30.

PoC pública

Anthropic's own exploit is not public: it reports a two-stage chain that leaks a kernel address to defeat KASLR and then overwrites a callback pointer to run a command as root, taking about 53 minutes in its test (48 for the leak, 5 for execution). It published no code, kernel version or configuration, and Ubuntu says the exploit is unreleased and no other is known. A separate proof-only repository on GitHub, whose publisher the articles do not name, triggers the race and detects the kernel echoing freed memory in a SYN-ACK, but does not implement code execution. Public maturity is verification only, yet Anthropic's claim shows a working exploit is feasible, so internet-facing hosts should be patched urgently.

Explicação gerada por IA a partir da matéria e dos artigos, em 04/11/2026 00:26.

Detalhes técnicos

  • In tcp_v4_syn_recv_sock(), ownership of ireq->ireq_opt passes to the child socket (newinet->inet_opt) without copying. Another CPU may be handling a retransmitted SYN and building a SYNACK via tcp_check_req(), tcp_v4_send_synack() and inet_csk_route_req() under rcu_read_lock() only. ip_build_and_send_pkt() and ip_options_build() then read opt->optlen twice (bleepingcomputer.com, fortiguard.fortinet.com).
  • inet_sock_destruct() frees inet_opt with a plain kfree(), and TCP child sockets lack SOCK_RCU_FREE. This produces a use-after-free in ip_options_build(). The overlap became possible after commit 079096f103fa, which stopped handling request sockets under the listener lock (gbhackers.com, fortiguard.fortinet.com).
  • A related race exists in request socket migration with net.ipv4.tcp_migrate_req=1 or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE program. reqsk_timer_handler() clones the request socket via inet_reqsk_clone(), so the old and cloned sockets share ireq_opt, and tcp_v4_reqsk_destructor() also uses a plain kfree() (fortiguard.fortinet.com).
  • The kernel CVE team's scenario sends a connection request carrying IPv4 Record Route or Timestamp options and retransmits it to win the race. The result can be memory disclosure, corruption or a crash (thehackernews.com).
  • IPv6 is unaffected by the main race because options are copied. A similar IPv6 variant tied to CALIPSO will be fixed in a separate patch (fortiguard.fortinet.com, aikido.dev). macOS (XNU) and RHEL 7 are not affected (bleepingcomputer.com). AWS Lambda is not affected (aikido.dev).
  • Anthropic's two-stage exploit first leaks a kernel address to defeat KASLR, then overflows a buffer to overwrite a callback pointer with an attacker-staged payload, running a shell command as root. A lost race fails only that connection and does not crash the system, so attempts can be repeated. In testing, the leak took 48 minutes and code execution 5 more, about 53 minutes in total (thehackernews.com, bleepingcomputer.com, gbhackers.com). Anthropic published no exploit code, kernel version or test configuration. Proof-only code on GitHub triggers the race and detects the kernel echoing freed memory in a SYN-ACK but does not implement code execution (thehackernews.com).
  • Broader context: the same Anthropic disclosure covered four other chains: Chrome (V8 memory corruption, V8 sandbox escape, CacheStorage race, FedCM use-after-free), Safari (same-origin policy disabled via memory read/write), a locked Google Pixel 9 (USB/pairing bypass) and a Windows HTTP/3 denial-of-service tracked as CVE-2026-33096 (thehackernews.com, gbhackers.com). Anthropic's central claim is that one model found and combined separate bugs with little human involvement; this rests on Anthropic's own account and the model is not named. No IOCs or exploit code were published (thehackernews.com, darkreading.com). Darkreading.com frames it as a dual-use milestone that shortens the window between patch and weaponization.
  • MPTCP is not normally enabled by default. Since Go 1.24, however, the Go runtime enables MPTCP on Linux TCP listeners when the kernel supports it, so some Go services may expose MPTCP listeners unknowingly (bleepingcomputer.com, aikido.dev). AlmaLinux and CloudLinux ship with MPTCP off by default (aikido.dev).
  • Ubuntu states the vulnerability is not specific to MPTCP, though the Anthropic exploit reportedly uses it (gbhackers.com).
  • Red Hat published an nftables rule on October 30 that drops inbound IPv4 TCP packets carrying IP options; it blocks the known trigger but cannot fully prevent exploitation and may break workloads relying on IPv4 options. A CIQ kernel team member noted on the oss-security mailing list that the filter applies only at the host level and can be bypassed by traffic between containers on the same host (thehackernews.com).

Remediação

  • Install vendor-fixed kernels and reboot. AWS says this is the only complete fix and that a livepatch also resolves it (aikido.dev). gbhackers.com reports the fix is in all maintained stable kernels.
  • Self-built kernels should move to 5.10.272, 5.15.223, 6.1.190, 6.6.159, 6.12.113, 6.18.56, 7.2.10 or 7.3. The kernel CVE team recommends the latest stable kernel rather than cherry-picking (thehackernews.com).
  • The upstream fix replaces kfree() with kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor() (gbhackers.com, fortiguard.fortinet.com).
  • Debian fixed the flaw in 6.1.190-1 (Bookworm) and 6.12.113-1 (Trixie) (bleepingcomputer.com).
  • Amazon Linux 2 and 2023 have patched kernels (4.14 to 6.18). Update EKS nodes to AMI release v20261031 or later and ECS on EC2 to ECS-optimized AMI 20261031. Fargate tasks launched after November 1, 2026 6:00 AM PDT use the patched platform. Bottlerocket AMIs were expected from November 2 (aikido.dev).
  • AWS recommends updating instances within 30 days and gave an iptables rule dropping IPv4 packets with IP options. It also issued exposure guidance for front-end services (ALB, NLB, CloudFront) (aikido.dev).
  • Red Hat shipped fixed kernels for RHEL 8, 9 and 10 on November 1 via RHSA-2026:93414, RHSA-2026:93412 and RHSA-2026:93413; a reboot is required after installation (thehackernews.com).
  • Ubuntu fixes for 22.04 LTS and newer remain in the -proposed pocket as of November 2, with no release date to the default channel. Administrators needing the fix urgently can enable -proposed and install updated kernel-meta packages with apt install -t <release>-proposed --only-upgrade, then reboot. Ubuntu's public tracker still lists several builds as work in progress, so verify before assuming a release is patched. Canonical says this route suits teams with their own acceptance tests, and its new kernel strategy shortens SRU cycles to two weeks with weekly kernel releases (gbhackers.com, thehackernews.com).
  • Ubuntu 20.04 LTS and older need Ubuntu Pro: ESM for 20.04 and 18.04, ESM with the Legacy add-on for 16.04 and 14.04 (gbhackers.com). Earlier reports listed 20.04, 18.04 and 16.04 as vulnerable and unfixed (bleepingcomputer.com, aikido.dev).
  • Rocky Linux 8, 9 and 10 are affected with fixes pending (bleepingcomputer.com, thehackernews.com).
  • Interim mitigations: restrict access to trusted networks or IPs. CIQ and Red Hat recommend nftables rules dropping IPv4 TCP packets that carry IP options, but these only apply per-host and can be bypassed by container-to-container traffic on the same host, reduce but do not fully prevent exploitation, and may break connections relying on IPv4 options (bleepingcomputer.com, thehackernews.com, gbhackers.com). Disabling MPTCP alone is not sufficient because ordinary TCP can still trigger the bug (bleepingcomputer.com). The Go Security Team calls per-program MPTCP disabling fragile (aikido.dev).
  • Wider guidance from the Anthropic disclosure: also apply the other vendor patches (Chrome 156 or later, iOS/iPadOS 26.5.2 or later, the Windows update for CVE-2026-33096, the Google Android fix), shorten patch cycles and assume less time between disclosure and exploitation, and favor exploit-mitigation hardening such as memory safety and sandboxing over patch speed alone (thehackernews.com, gbhackers.com, darkreading.com).

Relatos divergentes

  • Severity: The kernel CVE team scores it 9.8 (thehackernews.com), and gbhackers.com also reports CVSS 3.1 9.8 for Ubuntu. Red Hat initially scored it 5.9 Moderate on its CVE page and 8.1/Important in its machine-readable advisory, citing a hard-to-win race and potential denial of service, but has since raised its own score to 9.8 Critical in its November 1 advisories (thehackernews.com). SUSE scores it 8.1, Amazon 7.0, and Oracle also lower (thehackernews.com, bleepingcomputer.com). The 9.8 figure rests on both sides of the race being attacker-induced.
  • Exploitability: Anthropic says its model produced a working remote root exploit on MPTCP listeners, and AWS confirms RCE is possible under specific conditions (aikido.dev). The latest Ubuntu report (gbhackers.com) says the flaw can lead to remote code execution but that Anthropic's exploit is unreleased, whereas an earlier reading of Ubuntu's advisory described crashes and service disruption without confirming a reliable remote exploit. CloudLinux's kernel team says it could not reproduce Anthropic's claim, and no exploit or configuration was published (aikido.dev). RCE has not been publicly demonstrated without an MPTCP listener (bleepingcomputer.com), though the Go Security Team notes that systems without MPTCP listeners may be open to similar attacks (aikido.dev).
  • Mitigations: Red Hat initially said no mitigation met its deployability standards, and advisories did not say whether disabling MPTCP or blocking IP-option packets reduces risk (thehackernews.com). Subsequent reports from CIQ, AWS and Red Hat itself give packet-filtering rules for IP options, though a CIQ kernel team member notes the nftables rule only protects at the host level and can be bypassed by container traffic (bleepingcomputer.com, aikido.dev, thehackernews.com). Ubuntu's security team says security updates are the only appropriate mitigation and that some sources' advice to disable MPTCP is wrong because the flaw is not MPTCP-specific (gbhackers.com).
  • Exploitation status: As of October 29, no vendor advisory reported in-the-wild attacks (aikido.dev), and none was confirmed as of October 30 (bleepingcomputer.com, thehackernews.com). The Fortinet advisory states no active exploitation (fortiguard.fortinet.com). The flaw was not in CISA's KEV catalog as of its October 30 release (thehackernews.com). Anthropic's exploits were built in the lab and not seen in real attacks (thehackernews.com).
  • Upstream fix date: One thehackernews.com report says the fix landed upstream on October 5; another thehackernews.com report on Anthropic's disclosure says October 15. The input does not resolve which is correct.
  • Patch status: gbhackers.com says the flaw is patched in all maintained stable kernels, but Ubuntu fixes remained in -proposed and Rocky Linux fixes were pending as of November 2 (gbhackers.com, thehackernews.com, bleepingcomputer.com). The vendor-specific status is the more recent and precise.
  • Component description: Anthropic describes the bug as a multipath TCP issue, but the public record describes an IPv4 TCP fix, not MPTCP specifically (thehackernews.com), consistent with Ubuntu's statement that it is not MPTCP-specific (gbhackers.com).
  • Autonomy of the model: darkreading.com says the model worked autonomously, while thehackernews.com says the human role at each step is not disclosed and the claim rests only on Anthropic's account.

Linha do tempo

  1. thehackernews.com ↗ · pub. 03/11/2026 08:23 · coletado 03/11 10:00

    Red Hat Ships Critical Patches for Linux Kernel TCP Use-After-Free CVE-2026-98432; Ubuntu Fixes Remain in Testing Channel

    This article reports that Red Hat has now shipped fixed kernels for CVE-2026-98432 on November 1 (RHSA-2026:93414, RHSA-2026:93412, RHSA-2026:93413 for RHEL 8/9/10), superseding the earlier status of "fixes pending" for RHEL, and confirms Red Hat raised its internal severity score from 5.9 Moderate to 9.8 Critical. It also adds detail on Ubuntu's `-proposed` testing pocket fixes (as of November 2, still not in the default channel) with specific apt commands for manual installation, details Red Hat's nftables mitigation rule published October 30, and notes a CIQ kernel team member's observation on oss-security that the nftables rule only protects at the host level and can be bypassed by container-to-container traffic. It also confirms the flaw was not in CISA's KEV catalog as of October 30.

    ler a análise desta fonte

    This article reports that Red Hat has now shipped fixed kernels for CVE-2026-98432 on November 1 (RHSA-2026:93414, RHSA-2026:93412, RHSA-2026:93413 for RHEL 8/9/10), superseding the earlier status of "fixes pending" for RHEL, and confirms Red Hat raised its internal severity score from 5.9 Moderate to 9.8 Critical. It also adds detail on Ubuntu's -proposed testing pocket fixes (as of November 2, still not in the default channel) with specific apt commands for manual installation, details Red Hat's nftables mitigation rule published October 30, and notes a CIQ kernel team member's observation on oss-security that the nftables rule only protects at the host level and can be bypassed by container-to-container traffic. It also confirms the flaw was not in CISA's KEV catalog as of October 30.

    Red Hat has released fixed kernels for CVE-2026-98432, a use-after-free race condition in the Linux kernel's IPv4 TCP connection setup path, now rated 9.8/10 Critical by Red Hat after an earlier 5.9 Moderate score. Advisories RHSA-2026:93414 (RHEL 8), RHSA-2026:93412 (RHEL 9), and RHSA-2026:93413 (RHEL 10) shipped November 1, requiring a reboot. Ubuntu's fixes for 22.04, 24.04, and 26.04 LTS remain in the opt-in -proposed testing pocket as of November 2, with no release date to the regular update channel. The flaw is remotely exploitable without authentication via crafted IPv4 TCP options and has not been observed exploited in the wild or added to CISA's KEV catalog.

    Technical Details

    The kernel passes IP options (Record Route or Timestamp) from an incoming TCP SYN to the new socket without copying them; a retransmitted connection request racing another CPU reading those options can trigger a read of freed memory. IPv6 is unaffected on the main path. A member of the CIQ kernel team noted on the oss-security mailing list that Red Hat's published nftables mitigation rule (dropping inbound IPv4 TCP packets with IP options) only applies per-host and can be bypassed by container-to-container traffic on the same host.

    Remediation

    Administrators should install the Red Hat advisories and reboot. Ubuntu users needing the fix before general release can enable the -proposed pocket and install the updated kernel-meta packages manually, then reboot. Ubuntu 20.04 and older require Expanded Security Maintenance via Ubuntu Pro. Canonical reiterated that disabling MPTCP alone is insufficient since the flaw lies in standard IPv4 TCP handling, not MPTCP, and that security updates are the only appropriate mitigation.

  2. gbhackers.com ↗ · pub. 03/11/2026 06:33 · coletado 03/11 08:00

    Ubuntu publishes -proposed kernel fixes for CVE-2026-98432, a critical Linux IPv4 TCP use-after-free (CVSS 9.8)

    Ubuntu fixes now exist in the -proposed pocket for 22.04 LTS and newer but are not yet in default updates. Older releases need Ubuntu Pro (ESM). Ubuntu's security team rejects disabling MPTCP as a mitigation, says Anthropic's exploit is still unreleased, and notes the CVE page lists an nftables rule that only partly reduces risk.

    ler a análise desta fonte

    Ubuntu fixes now exist in the -proposed pocket for 22.04 LTS and newer but are not yet in default updates. Older releases need Ubuntu Pro (ESM). Ubuntu's security team rejects disabling MPTCP as a mitigation, says Anthropic's exploit is still unreleased, and notes the CVE page lists an nftables rule that only partly reduces risk.

    Ubuntu (Canonical) has published fixes for CVE-2026-98432, a use-after-free in the Linux kernel IPv4 TCP connection handling, scored CVSS 3.1 9.8 with possible remote code execution. Fixes for Ubuntu 22.04 LTS and newer are only in the -proposed pocket, not yet in the default updates channel, and Ubuntu's public tracker still lists several builds as work in progress. Ubuntu says the exploit Anthropic generated remains unreleased and reportedly uses Multipath TCP (MPTCP), but the flaw is not MPTCP-specific and no other exploit is known. Ubuntu's security team says security updates are the only appropriate mitigation, not disabling MPTCP.

    Technical Details

    • tcp_v4_syn_recv_sock() passes ownership of ireq->ireq_opt to the child socket without copying it.
    • Another CPU handling a retransmitted SYN can build a SYNACK while the child socket's options are freed. Nothing prevents the race since the kernel stopped holding the listener lock for request sockets.
    • A plain kfree() leaves a dangling pointer in ip_options_build(). The upstream fix uses kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor().
    • IPv6 is not affected by the first issue.
    • The article compares it to the SCTPhantom use-after-free and notes about 440 kernel CVE advisories were published in 24 hours.

    Remediation

    • Enable the -proposed pocket per Ubuntu's instructions, install explicitly with apt install -t <release>-proposed, then reboot. Check uname -r and dpkg -l 'linux-image*' | grep ^ii against Ubuntu's table.
    • Canonical says this route suits teams with their own acceptance tests. Under its new kernel strategy SRU cycles shrink to two weeks, with weekly kernel releases.
    • Ubuntu 20.04 LTS and older need Ubuntu Pro: ESM for 20.04 and 18.04, ESM with the Legacy add-on for 16.04 and 14.04.
    • The CVE page lists an interim nftables rule dropping incoming IPv4 TCP packets with IP options. It reduces risk but does not fully prevent exploitation and breaks connections relying on IPv4 options.
    • Prioritize internet-facing Ubuntu servers and test the proposed kernels now.
  3. fortiguard.fortinet.com ↗ · pub. 02/11/2026 05:00 · coletado 02/11 14:01

    Fortinet PSIRT advisory FG-IR-26-188 describes Linux kernel IPv4 TCP use-after-free (CVE-2026-98432)

    ler a análise desta fonte

    Fortinet PSIRT published advisory FG-IR-26-188 on 2026-11-02 for CVE-2026-98432, a use-after-free in the Linux kernel IPv4 TCP stack (inet_opt / ireq_opt handling). The article does not specify which Fortinet products are affected. It does not state active exploitation, a CVSS score, fixed versions or attribution. IPv6 is not affected by the first issue, and the IPv6 migration variant tied to CALIPSO will be fixed in a separate patch.

    Technical Details

    • tcp_v4_syn_recv_sock() transfers ownership of ireq->ireq_opt to the child socket without copying it. Another CPU can concurrently handle a retransmitted SYN for the same request socket and send a SYNACK from tcp_check_req().
    • tcp_v4_send_synack() and inet_csk_route_req() read ireq->ireq_opt under rcu_read_lock() only, and ip_build_and_send_pkt() / ip_options_build() read opt->optlen twice.
    • Since commit 079096f103fa, request sockets are processed without the listener lock, so the child socket can be freed while the SYNACK is still being built. TCP child sockets lack SOCK_RCU_FREE, and inet_sock_destruct() frees inet_opt with a plain kfree(), causing a use-after-free in ip_options_build().
    • A similar issue exists with request socket migration (net.ipv4.tcp_migrate_req=1 or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE program). reqsk_timer_handler() clones the request socket via inet_reqsk_clone(), so the old and cloned sockets share ireq_opt, and tcp_v4_reqsk_destructor() also uses a plain kfree().
    • The fix described uses kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor(), consistent with other paths that replace inet_opt.

    Remediation

    The article gives no fixed versions and does not specify which Fortinet products are affected. Defenders should consult the FG-IR-26-188 advisory for affected products and apply the fix described (kfree_rcu() in the two destructors) once it is available in their kernel.

  4. aikido.dev ↗ · pub. 02/11/2026 06:00 · coletado 02/11 08:01

    CVE-2026-98432: Linux kernel IPv4 TCP use-after-free (9.8) fix guide, AWS patches and interim mitigations

    Aikido adds AWS-specific remediation (Amazon Linux, EKS AMI v20261031, ECS AMI 20261031, Fargate platform after November 1, Bottlerocket), an AWS iptables rule dropping IPv4 packets with IP options, exposure guidance for AWS front-end services (ALB, NLB, CloudFront; AWS recommends updating instances within 30 days), and notes that AWS Lambda is not affected. It also reports CloudLinux could not reproduce Anthropic's claim, that AlmaLinux and CloudLinux ship MPTCP off by default, and that the Go Security Team calls per-program MPTCP disabling fragile.

    ler a análise desta fonte

    Aikido adds AWS-specific remediation (Amazon Linux, EKS AMI v20261031, ECS AMI 20261031, Fargate platform after November 1, Bottlerocket), an AWS iptables rule dropping IPv4 packets with IP options, exposure guidance for AWS front-end services (ALB, NLB, CloudFront; AWS recommends updating instances within 30 days), and notes that AWS Lambda is not affected. It also reports CloudLinux could not reproduce Anthropic's claim, that AlmaLinux and CloudLinux ship MPTCP off by default, and that the Go Security Team calls per-program MPTCP disabling fragile.

    CVE-2026-98432 is a use-after-free race in how the Linux kernel handles IPv4 TCP connection setup, present since kernel 4.4. The kernel CVE team rates it 9.8. Anthropic reports that an unreleased Claude research model wrote an exploit giving unauthenticated remote root on Linux servers with an MPTCP listener. AWS confirms that under specific conditions a remote, unauthenticated attacker could achieve remote code execution. As of October 29, no vendor advisory reported in-the-wild attacks. This Aikido guide focuses on remediation and exposure by environment.

    Technical Details

    During the TCP handshake the kernel keeps the SYN's IP options with the request socket. In tcp_v4_syn_recv_sock() the child socket takes ownership of those options without copying them. If another CPU is building a SYNACK for a retransmitted SYN, the options can be freed while still in use, causing a use-after-free in ip_options_build(). Request socket migration (net.ipv4.tcp_migrate_req=1 or a BPF reuseport migrate program) opens a similar path. IPv6 is not affected by the main race because options are copied; a similar CALIPSO-related IPv6 issue is being fixed in a separate patch. The upstream fix switches the frees to kfree_rcu(). Anthropic's test took 48 minutes to leak a kernel address and 5 more to reach command execution; a lost race fails only that handshake, so retries are possible. Anthropic did not publish the exploit, kernel version or configuration, and CloudLinux's kernel team says it could not reproduce the claim. The Go Security Team notes that systems without MPTCP listeners may be open to similar attacks, and that Go 1.24+ requests MPTCP listeners by default where the kernel allows it. Some distributions such as AlmaLinux and CloudLinux ship with MPTCP off.

    Remediation

    Install a patched kernel and reboot; AWS says this is the only complete fix and that a livepatch also resolves it. Amazon Linux 2 and 2023 have patched kernels (4.14 to 6.18). EKS nodes should move to AMI release v20261031 or later, ECS-optimized AMI release 20261031 applies to ECS on EC2, Fargate tasks launched after November 1, 2026 6:00 AM PDT use the patched platform, and Bottlerocket AMIs were expected from November 2. Ubuntu fixes were in progress for 22.04, 24.04, 26.04 and 26.10, with 20.04, 18.04 and 16.04 listed as vulnerable and unfixed; RHEL 8, 9 and 10 had no fixed kernel. Debian, Oracle Linux and SUSE have shipped fixes for at least some kernels. Upstream fixed versions are 5.10.272, 5.15.223, 6.1.190, 6.6.159, 6.12.113, 6.18.56, 7.2.10 and 7.3. Interim measures: disable MPTCP (net.mptcp.enabled=0, GODEBUG=multipathtcp=0), a weak control; drop IPv4 packets with IP options (iptables -I INPUT 1 -m u32 --u32 '0>>24&0x0f=6:15' -j DROP, or an AWS Network Firewall equivalent); or place the host behind a separate load balancer that terminates TCP. A proxy on the same host does not help. Verify the running kernel after reboot against the vendor's fixed version.

  5. bleepingcomputer.com ↗ · pub. 30/10/2026 18:09 · coletado 30/10 19:00

    Linux kernel CVE-2026-98432 TCP use-after-free: Anthropic AI exploit gives remote root on MPTCP servers; Ubuntu and RHEL unpatched

    BleepingComputer adds CIQ's interim mitigation (nftables rules blocking IPv4 TCP packets with IP options, with a warning that disabling MPTCP alone is insufficient), the fact that Go 1.24+ enables MPTCP listeners by default, the confirmed Debian fixed versions, the affected status of Rocky Linux 8/9/10 and RHEL 8/9/10 (RHEL 7 unaffected), and that Ubuntu remained vulnerable as of October 30.

    ler a análise desta fonte

    BleepingComputer adds CIQ's interim mitigation (nftables rules blocking IPv4 TCP packets with IP options, with a warning that disabling MPTCP alone is insufficient), the fact that Go 1.24+ enables MPTCP listeners by default, the confirmed Debian fixed versions, the affected status of Rocky Linux 8/9/10 and RHEL 8/9/10 (RHEL 7 unaffected), and that Ubuntu remained vulnerable as of October 30.

    A critical use-after-free in the Linux kernel's IPv4 TCP code, tracked as CVE-2026-98432 (9.8 from the Linux kernel CVE team), allows unauthenticated remote code execution as root on servers with a Multipath TCP (MPTCP) listener. Researchers at Anthropic reported that an unreleased Claude model built an exploit that bypassed KASLR and ran arbitrary commands as root in about 53 minutes. The flaw also affects ordinary TCP, although RCE has not been publicly demonstrated without an MPTCP listener. Red Hat rates it only 5.9 (potential denial of service) because the race is hard to win. Fixes exist upstream and in some distributions, but Ubuntu and RHEL remained unpatched as of October 30, and no in-the-wild exploitation has been confirmed.

    Technical Details

    The bug is a race in which tcp_v4_syn_recv_sock() hands ireq->ireq_opt to the child socket (newinet->inet_opt) without copying it. Another CPU can process a retransmitted SYN and send a SYNACK via tcp_check_req(), tcp_v4_send_synack() and inet_csk_route_req() under rcu_read_lock() only, after which ip_build_and_send_pkt() and ip_options_build() read opt->optlen twice. A similar issue occurs during request socket migration when net.ipv4.tcp_migrate_req is enabled or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE program is used. Affected kernels date back to 4.4. MPTCP is not normally enabled by default, but since Go 1.24 the runtime enables MPTCP on Linux TCP listeners when the kernel supports it, so some Go services may expose MPTCP listeners unknowingly. macOS (XNU) is not affected, and RHEL 7 is not affected because it lacks the vulnerable code.

    Remediation

    Install updated kernel packages as distributions release them. Debian fixed the flaw in 6.1.190-1 (Bookworm) and 6.12.113-1 (Trixie), and Oracle Linux, Amazon Linux and SUSE have fixed some kernel versions. Ubuntu 22.04, 24.04, 26.04 LTS and 26.10 remain vulnerable with fixes in progress, and RHEL 8, 9 and 10 plus Rocky Linux 8, 9 and 10 are affected with fixes pending. Where no patch exists, restrict access to trusted networks or IPs. CIQ recommends temporarily dropping IPv4 TCP packets carrying IP options with nftables rules, and warns that disabling MPTCP alone is insufficient because ordinary TCP can still trigger the bug.

  6. gbhackers.com ↗ · pub. 30/10/2026 03:59 · coletado 30/10 04:00

    Ubuntu advisory details CVE-2026-98432 Linux kernel IPv4 TCP use-after-free; generic kernels still unpatched

    Adds Ubuntu's own advisory timeline (published October 15, updated October 29, 2026) and precise code-level detail: the faulty ownership transfer in tcp_v4_syn_recv_sock(), the kfree() in inet_sock_destruct() racing RCU readers in ip_options_build(), the role of commit 079096f103fa, and a second race in request socket migration with net.ipv4.tcp_migrate_req=1 or BPF_SK_REUSEPORT_SELECT_OR_MIGRATE. It also specifies the upstream fix (kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor()) and names the Ubuntu releases still awaiting fixes (26.10, 26.04 LTS, 24.04 LTS, 22.04 LTS generic plus cloud variants). Ubuntu's framing emphasizes crash/DoS impact and does not confirm a reliable remote exploit.

    ler a análise desta fonte

    Adds Ubuntu's own advisory timeline (published October 15, updated October 29, 2026) and precise code-level detail: the faulty ownership transfer in tcp_v4_syn_recv_sock(), the kfree() in inet_sock_destruct() racing RCU readers in ip_options_build(), the role of commit 079096f103fa, and a second race in request socket migration with net.ipv4.tcp_migrate_req=1 or BPF_SK_REUSEPORT_SELECT_OR_MIGRATE. It also specifies the upstream fix (kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor()) and names the Ubuntu releases still awaiting fixes (26.10, 26.04 LTS, 24.04 LTS, 22.04 LTS generic plus cloud variants). Ubuntu's framing emphasizes crash/DoS impact and does not confirm a reliable remote exploit.

    Ubuntu published and then updated (October 15 and October 29, 2026) an advisory for CVE-2026-98432, a use-after-free in the Linux kernel's IPv4 TCP connection handling rated 9.8 CVSS. The flaw stems from tcp_v4_syn_recv_sock() transferring ownership of IP options from a request socket's ireq->ireq_opt to a child socket without copying, while another CPU may still read those options when building a SYNACK for a retransmitted SYN. Ubuntu's description notes crashes and service disruption but does not claim a reliable remote exploit or active exploitation. Ubuntu's tracker lists generic kernels for 26.10, 26.04 LTS, 24.04 LTS and 22.04 LTS as vulnerable with fixes still in progress, along with older releases and several cloud kernel variants.

    Technical Details

    inet_sock_destruct() frees inet_opt with plain kfree(), so concurrent RCU readers in ip_options_build() — reached via tcp_check_req(), tcp_v4_send_synack() and inet_csk_route_req() — can touch freed memory. The overlap became possible once request sockets stopped being handled under the listener lock (commit 079096f103fa). A related race affects request socket migration when net.ipv4.tcp_migrate_req=1 or a BPF_SK_REUSEPORT_SELECT_OR_MIGRATE program is used, since cloned request sockets briefly share ireq_opt.

    Remediation

    The upstream fix replaces immediate deallocation with kfree_rcu() in inet_sock_destruct() and tcp_v4_reqsk_destructor(), deferring reclamation until RCU readers finish. Ubuntu users should track the advisory and not mistake listed target builds for released security updates.

  7. darkreading.com ↗ · pub. 29/10/2026 15:15 · coletado 29/10 16:00 só resumo do feed

    Anthropic says unreleased Claude model autonomously discovered and chained exploits in Chrome, Safari, Android, Windows and Linux

    ler a análise desta fonte

    Anthropic disclosed that an unreleased version of its Claude model was able to autonomously discover and chain multiple vulnerabilities across major platforms, including Google Chrome, Apple Safari, Android, Windows and Linux. According to the company, the model moved beyond single bug discovery to building working exploit chains, a capability threshold that materially lowers the cost of offensive operations. The disclosure is framed as a dual-use milestone: the same capability can accelerate defensive vulnerability research and patching, but also empowers less-skilled attackers. No specific CVEs, victims or in-the-wild abuse were reported in the article. Defenders should treat this as a signal that AI-assisted exploit development is maturing, shortening the window between patch release and weaponization.

    Technical Details

    • The model reportedly performed vulnerability discovery and exploit chaining across browsers and operating systems rather than isolated proof-of-concept bugs.
    • Platforms cited: Chrome, Safari, Android, Windows, Linux.
    • The model version involved is unreleased, and no indicators of compromise or exploit code were published.

    Remediation

    • Compress patching cycles for browsers and OS platforms; assume reduced time-to-exploit after disclosure.
    • Invest in exploit-mitigation hardening (memory-safety features, sandboxing, browser isolation) rather than relying on patch latency.
    • Monitor AI vendor safety disclosures and incorporate AI-assisted offensive capability into threat models.
  8. thehackernews.com ↗ · pub. 29/10/2026 12:57 · coletado 29/10 14:00

    CVE-2026-98432: Linux kernel IPv4 TCP use-after-free rated 9.8; AI-written root exploit demoed, Ubuntu and RHEL unpatched

    ler a análise desta fonte

    A race condition in the Linux kernel's IPv4 TCP connection setup path, tracked as CVE-2026-98432, allows a use-after-free when IP options stored with a pending request are handed to a new socket without being copied. The kernel CVE team scored it 9.8 CVSS (low attack complexity, both sides of the race attacker-induced), while Red Hat (5.9 Moderate on its CVE page, 8.1/Important in its machine-readable advisory), Oracle, SUSE (8.1) and Amazon (7.0) score it lower. Anthropic disclosed on October 27 that its Claude model wrote a working exploit achieving unauthenticated remote root on Linux servers running a multipath TCP (MPTCP) listener. The bug was introduced in Linux 4.4, fixed upstream on October 5 and credited to Anthropic researcher Xinyang Ge. As of October 29, Ubuntu and RHEL had not shipped fixed kernels and no in-the-wild exploitation was reported.

    Technical Details

    During the TCP handshake, when a connection completes the kernel passes the IP options from the pending request to the new socket by reference. If that socket is destroyed while another CPU is still using those options to answer a retransmitted SYN, the kernel reads freed memory. IPv6 is unaffected because options are copied. The kernel CVE team's scenario involves sending a connection request carrying IPv4 Record Route or Timestamp options and retransmitting it to win the race, leading to kernel memory disclosure, corruption or crash. Anthropic's two-stage exploit first leaks a kernel address to defeat KASLR, then overflows a buffer to overwrite a callback pointer with an attacker-staged payload, executing a shell command as root. A lost race only fails that connection, allowing repeated attempts; in testing the leak took 48 minutes and code execution 5 more. No exploit code, kernel version or test configuration was published.

    Remediation

    Install fixed vendor kernels where available (Debian, Oracle Linux, SUSE, Amazon Linux have shipped at least some fixed packages). Self-built kernels should move to 5.10.272, 5.15.223, 6.1.190, 6.6.159, 6.12.113, 6.18.56, 7.2.10 or 7.3; the kernel CVE team recommends updating to the latest stable kernel rather than cherry-picking. Ubuntu (including cloud, FIPS and real-time kernels) and RHEL have no fix yet, with Red Hat stating fixes are deferred to a future update and that no mitigation meets its deployability standards. Advisories do not state whether disabling MPTCP or blocking inbound packets carrying IP options reduces risk.

  9. gbhackers.com ↗ · pub. 28/10/2026 09:51 · coletado 28/10 10:00

    Anthropic's unreleased Claude model chains flaws into working exploits for Chrome, Safari, Android, Windows and Linux

    The article adds detail not in the known report: the Safari chain works by changing only a security flag, an object size and a URL, and Apple acknowledged it the same day; the Android chain on a locked Pixel 9 (three bypasses plus a USB fallback path, fixed by Google); the Windows flaw was found by reverse engineering with Ghidra and Anthropic estimates several million exposed HTTP/3 servers; the Linux CVE-2026-98432 is patched in all maintained stable kernels; partners found at least 129,000 verified flaws between April and July 2026; and Anthropic recommends parallel scanning agents and pull-request-time scanning.

    ler a análise desta fonte

    The article adds detail not in the known report: the Safari chain works by changing only a security flag, an object size and a URL, and Apple acknowledged it the same day; the Android chain on a locked Pixel 9 (three bypasses plus a USB fallback path, fixed by Google); the Windows flaw was found by reverse engineering with Ghidra and Anthropic estimates several million exposed HTTP/3 servers; the Linux CVE-2026-98432 is patched in all maintained stable kernels; partners found at least 129,000 verified flaws between April and July 2026; and Anthropic recommends parallel scanning agents and pull-request-time scanning.

    Anthropic's Frontier Red Team disclosed on October 27, 2026 that an unreleased research model, Claude, developed working exploit chains against Chrome, Safari, Android, Windows and Linux, several needing little or no user interaction. Every flaw was reported to the affected vendor before publication. The most serious is a zero-click Linux chain that gives a remote, unauthenticated attacker root command execution on servers with a multipath TCP listener (CVE-2026-98432). The article stresses speed: skills once limited to a few expert teams can now be performed with little human help, and the same capability can aid attackers.

    Technical Details

    • Chrome: a V8 bug corrupts heap memory, a second flaw escapes the V8 memory sandbox and defeats ASLR, a CacheStorage race condition reveals the privileged process layout, and a use-after-free in FedCM gives the final sandbox escape. A PoC opened Calculator on macOS seconds after page load. Google assigned 62 CVEs, 13 of them sandbox escapes, all fixed in Chrome 156.
    • Safari: the chain lets any website bypass the same-origin policy, exposing history, cookies and logged-in sessions. It did not run arbitrary code; it only changed a security flag, an object size and a URL in memory. Apple acknowledged the report the same day and has shipped a fix.
    • Android: three flaws chained on a locked Google Pixel 9 skip the USB data block, the pairing authorization check and the six-digit code check, then a fallback path sends raw file bytes over USB to extract photos and personal data. Google has fixed it.
    • Windows: remote crash bug in kernel QUIC code (CVE-2026-33096). A few packets can crash and restart a server answering HTTP/3 requests. Anthropic estimates several million such servers face the internet. Claude found it by reverse engineering the binary with tools such as Ghidra.
    • Linux: a race condition leading to a kernel networking use-after-free. The exploit leaks a kernel address to defeat KASLR (48 minutes in the test), then overwrites a callback pointer and runs a shell command as root in about five more minutes. Failed attempts do not crash the system, so retries are possible. CVE-2026-98432 is patched in all maintained stable kernels.
    • Anthropic's partners found at least 129,000 verified flaws between April and July 2026. Earlier this year a researcher showed Claude Opus helping build a working V8 exploit against an outdated Chromium build in Discord Desktop.

    Remediation

    • Apply current patches: Chrome 156 or later, the Apple Safari fix, the Pixel update, the Windows fix for CVE-2026-33096 and a patched stable Linux kernel for CVE-2026-98432.
    • Run many different scanning agents in parallel and scan code at pull request time. Anthropic released a free security-guidance plugin for Claude Code and is widening its Cyber Verification Program for vetted defenders.
  10. thehackernews.com ↗ · pub. 28/10/2026 05:15 · coletado 28/10 06:00 primeiro registro

    Anthropic's unreleased AI model chains flaws into working Chrome, Safari, Windows and Linux proof-of-concept exploits

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    Anthropic's Frontier Red Team reported that an unreleased internal research model found security flaws in Chrome, Safari, Android, Windows and Linux and chained them into five working proof-of-concept exploits. The exploits were built in the lab after prompting, were not seen in real attacks, and every flaw was reported to the vendor first, so all are patched. The key claim is that one model can find and combine several separate bugs with little human involvement. This rests on Anthropic's own account, since the article notes it does not break down what humans did at each step or name the model. Vendor credits (Google, Apple) can be verified, but the links between Anthropic's descriptions and the public CVE records for the Windows and Linux chains rest only on Anthropic's post.

    Technical Details

    • Chrome: four chained flaws. A V8 memory corruption, a V8 memory sandbox escape, a CacheStorage race condition that leaks the layout of the privileged browser process, and a use-after-free in FedCM give code execution outside the sandbox. Anthropic says it reported 62 CVE-assigned flaws fixed as of Chrome 156 (all critical or high, including 13 sandbox escapes). Google credits "Xinyang Ge of Anthropic, assisted by Claude" for specific fixes, not all 62. One PoC opened Calculator on a Mac within seconds of page load, with no clicks.
    • Safari: chain gives full read/write access to browser memory, then flips one value to disable the same-origin policy, exposing history, cookies and signed-in requests to other sites. Apple fixed the central use-after-free in iOS and iPadOS 26.5.2, crediting "Milad Nasr and Nicholas Carlini with Claude, Anthropic".
    • Windows: a denial-of-service via a few network packets, described by Anthropic as an out-of-bounds read in kernel QUIC handling. The public record for CVE-2026-33096 names HTTP.sys, rates it 7.5, and credits no finder. No open source ties the two descriptions to the same component. It was not marked exploited and not in the CISA KEV catalog as of late October.
    • Linux: the most severe chain gives unauthenticated remote root command execution, requiring a target running a multipath TCP listener. It leaks a kernel address to bypass KASLR, then reuses the same race condition to redirect execution to attacker-placed code. Anthropic reports 48 minutes to leak the address and 5 more to reach a root shell, and failed attempts do not crash the system, so retries are possible. Anthropic ties it to CVE-2026-98432 (kernel use-after-free, 9.8, fixed upstream October 15), but the public record describes an IPv4 TCP fix, not multipath TCP.

    Remediation

    • Apply current vendor patches: Chrome 156 or later, iOS/iPadOS 26.5.2 or later, the Windows update for CVE-2026-33096, and the upstream Linux kernel fix for CVE-2026-98432.
    • Anthropic follows a 90-day patch window plus 45 days before detailed disclosure, and offers vetted professionals access through its expanded Cyber Verification Program.