Microsoft's October 2026 Windows update enforces NTLMv1 SSO blocking by default, risking Wi-Fi, Ethernet and VPN authentication failures
The October 2026 Windows security update changes the default handling of NTLMv1-derived credentials for Single Sign-On. Before the update, Windows allowed them and logged warning events. Now they are blocked. Wi-Fi, Ethernet and VPN authentication may fail in environments that still depend on the legacy protocol. Microsoft states this is …