Windows Server 2016 August Update Can Trigger CompatTelRunner Crashes
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August 2026 update can trigger CompatTelRunner crashes on some Windows Server 2016 systems, with Microsoft confirming repeated 0xc0000409 errors linked to the Compatibility Appraiser service.
Microsoft says the August 2026 security update can cause the CompatTelRunner.exe process to repeatedly crash when the Compatibility Appraiser diagnostic service is enabled.
According to Service Alert WI1467310, affected Windows Server 2016 systems may record recurring Application Error events with exception code 0xc0000409.
CompatTelRunner.exe can repeatedly crash
CompatTelRunner.exe forms part of Windows Compatibility Telemetry and runs Microsoft Compatibility Appraiser tasks.
On affected Windows Server 2016 systems, the process may repeatedly crash and create Application Error entries in Event Viewer.
Microsoft says these events use Event ID 1000 and reference CompatTelRunner.exe alongside exception code 0xc0000409.
Physical servers and virtual machines are affected
The problem does not only affect physical Windows Server 2016 installations.
Microsoft says the crashes can also occur on virtual machines, including systems running in VMware environments and Microsoft Azure.
Administrators may therefore see recurring CompatTelRunner.exe errors across different Windows Server 2016 deployments after installing the August 2026 security update.
Microsoft says the crashes do not affect server functionality
Despite the repeated errors, Microsoft says the CompatTelRunner.exe crashes do not affect normal device functionality. The company has not provided a workaround.
Administrators can temporarily ignore the related Application event log warnings because Microsoft does not expect the crashes to interfere with server operation.
Microsoft is preparing a permanent fix
Microsoft says it is working on a resolution that will arrive through a future Windows update.
The company has not announced when it expects to release the fix.
The CompatTelRunner issue comes as Microsoft investigates other Windows Server problems. Windows Server 2025 is experiencing application and SQL Server crashes linked to memory-management changes.
Meanwhile, Microsoft’s latest September 2026 Patch Tuesday fixed 966 vulnerabilities, making it the company’s largest Patch Tuesday release to date.
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