As cited
Copy frozen at (site build).
vulnerabilities
August updates trigger 0xc0000409 errors on Windows Server 2016
Microsoft identified a regression in its August 2026 security update that causes 0xc0000409 errors on Windows Server 2016 systems with the Compatibility Appraiser diagnostic service enabled. The error appears to stem from compatibility issues introduced during patching. Microsoft has acknowledged the issue and provided guidance for affected organizations.
Why it matters: Windows Server 2016 administrators who applied August 2026 updates may experience service disruptions or crashes; review patch status and diagnostic service configuration to determine mitigation steps.
- Source published
- First seen by Cybersecurity Tracker