August updates trigger 0xc0000409 errors on Windows Server 2016
Microsoft says the August 2026 security update causes recurring CompatTelRunner.exe 0xc0000409 crashes on Windows Server 2016 with Compatibility Appraiser enabled; no functional impact.
Microsoft confirmed a known issue in which the August 2026 Windows security update generates recurring Application Error events (Event ID 1000, exception code 0xc0000409) in CompatTelRunner.exe on Windows Server 2016. The issue affects physical and virtual machines, including VMware and Azure environments, and per Microsoft does not affect device functionality. A permanent fix is planned for a future update, and the event log entries can be dismissed temporarily.
- Crashes occur on systems with the Compatibility Appraiser diagnostic service enabled
- Impacts physical and virtual machines, including VMware and Azure
- Microsoft says functionality is unaffected; fix coming in a future update
- Vendors
- Microsoft
From the original article
2 min read at bleepingcomputer.com
Microsoft says the August 2026 security update may trigger 0xc0000409 errors on Windows Server 2016 systems where the Compatibility Appraiser diagnostic service is enabled. [...]
By Sergiu Gatlan · bleepingcomputer.com
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