Bitcoin Core Discloses Three Flaws Affecting Block Creation, Tor Peers, and Compact Blocks
The Bitcoin Core team disclosed three patched Bitcoin Core vulnerabilities that affect block templates, Tor peer rules, and compact block sync. Tracked as CVE-2025-62861, CVE-2025-62860, and CVE-2025-62859, the bugs can halt mining nodes, expose Tor hosts, or stall block sync. Node operators on older builds must update to versions 30.0, 29.2, or 28.3 right away.
Bitcoin Core serves as the main software tool for checking transactions and mining blocks on the Bitcoin network. Therefore, bugs in mempool rules or peer handling put both miners and public routing nodes at high risk.
Entenda a falha
A vulnerabilidade
Three Bitcoin Core flaws, all fixed in 30.0, 29.2 and 28.3. CVE-2025-62861 (high) is a mempool bug in the version 3 (TRUC) transaction rules. After a chain reorg it can leave child transactions whose parent was evicted, so block template creation fails until a mining node is restarted. It affects 28.0 to 28.2 and 29.0 to 29.1. CVE-2025-62860 (medium) is in the -whitelist option: nodes with a local IP range whitelist gave trusted-peer rights to every inbound Tor peer. It affects all builds before 28.3, 29.2 and 30.0 that use -whitelist. CVE-2025-62859 (medium) is witness malleation in compact blocks: a malicious peer can make a node stall on block sync. The articles say only that it hits versions before 30.0 and 29.2.
Como funciona
For CVE-2025-62861, a reorg makes the node drop blocks and put their transactions back into the mempool with bypass_limits set to true. The TRUC sibling-eviction logic still runs during that re-add. It can evict a parent transaction while its children stay, and those children spend outputs that no longer exist. Block template creation then fails. For CVE-2025-62860, inbound Tor connections all appear to come from the Tor daemon's local IP, so a local-range whitelist matches every one of them. For CVE-2025-62859, a node receiving a compact block clears its download state before checking for witness malleation. If a bad peer announced a mutated block first, the node can only recover through a 10-minute GETDATA timeout.
Por que é vulnerável
CVE-2025-62861 came from a missing gate: the sibling-eviction branch was not conditioned on bypass_limits, so TRUC enforcement ran while reorged transactions were being re-added. CVE-2025-62860 came from a wrong assumption that a local IP identifies a trusted peer, when all inbound Tor peers share the Tor daemon's address. CVE-2025-62859 was an ordering error: download state was cleared before the malleation check. The fixes gate the TRUC checks on bypass_limits and make new builds never whitelist inbound Tor onion peers. The articles do not describe the fix for CVE-2025-62859.
Onde está
For CVE-2025-62861 the fix is Bitcoin Core pull request 33504, which gates the TRUC checks on bypass_limits; CVE-2025-62860 lies in the -whitelist option handling.
Como foi descoberta
The articles do not say who found the flaws or how. The Bitcoin Core team disclosed them through security advisories after patching. The developers say there are no attacks in the wild and no public exploit tools. They note that the Tor whitelist bug led to thousands of reachable mainnet nodes whitelisting all incoming Tor connections.
Explicação gerada por IA a partir da matéria e dos artigos, em 10/11/2026 21:15.
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Bitcoin Core Discloses Three Flaws Affecting Block Creation, Tor Peers, and Compact Blocks
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The Bitcoin Core team disclosed three patched Bitcoin Core vulnerabilities that affect block templates, Tor peer rules, and compact block sync. Tracked as CVE-2025-62861, CVE-2025-62860, and CVE-2025-62859, the bugs can halt mining nodes, expose Tor hosts, or stall block sync. Node operators on older builds must update to versions 30.0, 29.2, or 28.3 right away.
Bitcoin Core serves as the main software tool for checking transactions and mining blocks on the Bitcoin network. Therefore, bugs in mempool rules or peer handling put both miners and public routing nodes at high risk.