Windows 11 KB5124008 update breaks domain trust for some users

How to Resolve Windows 11 Error 1786 After KB5124008 Installation

Windows 11 update KB5124008 is causing domain trust failures and error 1786. Learn how to fix Active Directory login issues using registry workarounds.

Windows 11 KB5124008 update breaks domain trust for some users

Microsoft is investigating reports that the Windows 11 KB5124008 security update is breaking domain trust relationships on some enterprise systems, preventing users from logging in with valid domain credentials. [...]

Windows 11 KB5124008 Update Breaks Active Directory Domain Trust and Blocks User Logins

Microsoft is investigating reports that the Windows 11 KB5124008 security update is breaking Active Directory domain trust on some enterprise computers, leaving users unable to sign in with valid credentials. The problem appears linked to Machine Identity Isolation, although Microsoft has not confirmed the root cause or published an official workaround. Released on September 8, 2026, KB5124008 is a cumulative security update for Windows 11 versi…