Said It Here

KB5124008 breaking domain trust?

Update KB5124008 breaks domain trust and causes connection status to flip unpredictably between true and false even after rebooting, repairing trust, and disabling machine identity isolation. Because remediation remains inconsistent, administrators cannot confirm whether the fix is actually working for end users to log in.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    Manually running Test-ComputerSecureChannel -repair after trust breaks
  2. 2
    Disabling machine identity isolation via group policy or registry settings
  3. 3
    Checking domain controller replication health and configuring DNS forwarding zones

In their words

Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.

r/sysadmin2 people · September 2026

“KB5124008 - Breaking Domain Trust for anyone else?”source ↗

MrEMMDeeEMM · r/sysadmin · 32 upvotes

“It still returns false half the time after remediation.”source ↗

Gerane · r/sysadmin · 5 upvotes

“It flips back and forth true and false even after disabling machine identity isolation, rebooting, and repairing trust.”source ↗

Gerane · r/sysadmin · 1 upvotes

“What I don’t know, is if the mitigation is actually working for end users to log in.”source ↗

Gerane · r/sysadmin · 1 upvotes

Where this came up

People with this problem also raised