Microsoft August 2026 Update Triggers 0xc0000409 Errors on Windows Server 2016

According to reporting by BleepingComputer, Microsoft acknowledged that the August 2026 security update may trigger 0xc0000409 errors on Windows Server 2016 systems where the Compatibility Appraiser diagnostic service is enabled. The error code 0xc0000409 typically indicates a failed application initialization, and in this case, it is linked to the Compatibility Appraiser service, which assesses application compatibility during and after updates. The issue was reported on September 8, 2026, following the deployment of the August 2026 security updates. Microsoft has stated it is investigating the matter, but no official resolution or workaround has been published at this time. Affected users may experience prevented update installation or service disruptions. No exploitation of this issue has been reported; the problem is characterized as a compatibility conflict rather than a security vulnerability. Microsoft has not released a specific patch for this compatibility issue, and users encountering the error may need to disable the Compatibility Appraiser service or uninstall the update if it prevents system functionality.