Microsoft released Windows 11 update KB5127648 on October 13, 2026. Its notes say it is the last monthly update for 24H2 Home and Pro. It fixes Explorer crashes in shared setups such as Azure Virtual Desktop and FSLogix. It also fixes printing failures that began after the August update. The update also changes a default for NTLMv1, an old Windows sign-in method. A registry value named BlockNtlmv1SSO controls it. When that value is unset, Windows used to run in Audit mode (0). It now runs in Enforce mode (1), which stops Windows from creating NTLMv1-based credentials for single sign-on. This applies only where Credential Guard is off. Microsoft warns that Wi-Fi, Ethernet and VPN links built on MS-CHAPv2 logins might be affected.
Microsoft does not say how many devices could be hit. It does not name VPN products or describe what a failed login looks like. Its notes also do not explain what Audit mode did beyond naming it. Three other problems remain open. Smart App Control may be greyed out, and a fix is promised without a date. Non-admin Remote Desktop logins can fail where Administrator protection is on. Some USB Audio Class 1.0 devices still fail, and a September 14 patch fixed only part of that.
The change takes effect with no action from admins, so an unset value now decides the outcome. Teams that use MS-CHAPv2 logins on machines without Credential Guard can check both settings and test VPN, Wi-Fi and Ethernet sign-ins first. Owners of 24H2 Home and Pro devices get no further security updates.