Windows
Claude desktop stopped working after security update KB 5124008
Claude's desktop app was reported as unable to function after a known issue update. The security update KB 5124008 was uninstalled to roll the machine back until a fix is available.
Killed once by someone from XL.net, on 2026-09-11.
Affects
Apps
- Claude
What you see
- Claude desktop would not function after the update installed.
Why it happens
Likely Suspected compatibility issue from security update KB 5124008
When it shows up
Claude desktop stops functioning after security update KB 5124008 is installed on a Windows computer
You are in this case if:
- Security update KB 5124008 is present in installed updates
- Claude desktop is reported as unable to function after the update
1 fix below
The steps that killed it
The steps are behind a quick check
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Someone from XL.net killed this on a Windows computer on 2026-09-11. It is written up from that one repair, so it cites no outside page.