August 2026 Update Triggers CompatTelRunner.exe Errors on Windows Server 2016
Summary
Microsoft says the August 2026 security update can cause recurring CompatTelRunner.exe errors on Windows Server 2016 when Compatibility Appraiser is enabled. Device functionality is unaffected; a fix is planned for a future update.
Key points
- The August 2026 Windows security update may cause recurring 0xc0000409 errors associated with CompatTelRunner.exe when the Compatibility Appraiser service is enabled.
- Microsoft says the issue affects physical and virtual Windows Server 2016 systems, including VMware and Azure environments.
- The crashes may create recurring Application Error events (Event ID 1000), but Microsoft says they do not affect device functionality.
- Microsoft advises that the associated event log warnings can be dismissed temporarily while it works on a fix for a future update; no timeline has been provided.
Article Details
- Event Type
- Windows Server 2016 issue caused by an August 2026 security update
- Impact
- On affected systems with the Compatibility Appraiser diagnostic service enabled, CompatTelRunner.exe may crash repeatedly and generate Application Error events with code 0xc0000409. Microsoft says the issue affects physical devices and virtual machines, but does not impair device functionality.
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AzureThe issue affects physical and virtual machines, including VMware and Azure environments, and Microsoft plans to address it in a future update.CompatTelRunner.exeMicrosoft says the August 2026 security update can cause 0xc0000409 errors on Windows Server 2016 systems when the Compatibility Appraiser diagnostic service is enabled, leading to recurring CompatTelRunner.exe crashes.Microsoft Compatibility AppraiserMicrosoft Compatibility Appraiser, which controls CompatTelRunner and is a Windows Compatibility Telemetry component, is a background system task that checks if the device meets the hardware and software requirementsVMwareThe issue affects physical and virtual machines, including VMware and Azure environments, and Microsoft plans to address it in a future update.Windows Server 2016Microsoft says the August 2026 security update can cause 0xc0000409 errors on Windows Server 2016 systems when the Compatibility Appraiser diagnostic service is enabled, leading to recurring CompatTelRunner.exe crashes.