Networking problems after the October 2026 Windows update? NTLM might be to blame

The October 2026 Windows security update blocks NTLMv1-derived credentials for single sign-on by default, which could break Wi-Fi, Ethernet and VPN authentication for organizations still relying on the legacy protocol, The Register reports. Administrators can temporarily set the BlockNtlmSSO registry value to audit mode, though Microsoft says this should only be a scoped, temporary security exception.