Microsoft shares workaround for Windows domain login issues
Microsoft confirms September 2026 Windows updates trigger domain trust failures via Machine Identity Isolation and shares a workaround for Windows 11 enterprises.
Microsoft confirmed the September 2026 security updates (KB5124008 for Windows 11 24H2/25H2, KB5124012 for 26H1) cause Windows to honor Machine Identity Isolation enforcement settings, breaking domain trust on systems not connected to Windows Server 2025 domain controllers. Admins report valid credentials failing with domain trust and credential errors. The workaround requires disabling Machine Identity Isolation via the same management method that enabled it (Intune, group policy, or registry) and resetting the secure channel with Test-ComputerSecureChannel. Microsoft previously shipped out-of-band fixes for Remote Desktop, Hyper-V, and USB audio issues from the same updates.
- Updates KB5124008 and KB5124012 trigger the domain trust failures
- Machine Identity Isolation is only supported at Windows Server 2025 domain functional level
- Workaround: disable the feature and run Test-ComputerSecureChannel -Repair
- Permanent fix expected in a future Windows update
From the original article
2 min read at bleepingcomputer.com
Microsoft shared a temporary fix on Wednesday for a known issue that prevents Windows 11 users from logging in with valid domain credentials after installing the September 2026 security updates. [...]
By Sergiu Gatlan · bleepingcomputer.com
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