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WINLOGON_FATAL_ERROR
Winlogon fatal error for WINLOGON_FATAL_ERROR
WINLOGON_FATAL_ERROR is bug check code 0xC000021A. Microsoft documents this as one of the few cases where a user-mode subsystem failure can shut down Windows, because Winlogon and CSRSS are required for the operating system to run securely.
How to read it in a dump
- The real failure is often in user mode, so a kernel debugger alone may not identify the initiating application or service.
- Mismatched or restored system files, third-party services, credential components, or subsystem compromise can be involved.
- The dump and event logs should identify whether Winlogon, CSRSS, or a dependent component terminated first.
What to check
- Check recent service, driver, security, credential-provider, and system-file changes.
- Collect user-mode dumps or event logs for Winlogon/CSRSS-related failures when available.
- Verify system file consistency and restore provenance before reinstalling or replacing random binaries.
References
- Bug Check 0xC000021A: WINLOGON_FATAL_ERROR
- Analyze a kernel-mode dump with WinDbg
- Microsoft Bug Check Code Reference
Dump evidence
Preserve the complete dump, the four bug-check parameters, the exact Windows build, loaded-module list, and the event timeline immediately before the stop. AllStat summarizes the condition as “This means that that the Winlogon process terminated unexpectedly.”; that sentence identifies the failure class, while the parameters and stack determine which object, driver, processor, or subsystem instance was involved.
Analysis order
- Run WinDbg
!analyze -v, then inspect the documented meaning of each parameter instead of relying only on the probably-caused-by line. - find the earliest abnormal event: driver update, firmware change, device reset, storage error, verifier report, resource exhaustion, or application hang connected with winlogon / fatal.
- keep third-party filter, security, storage, graphics, and virtualization drivers in the module inventory; removing evidence before dump analysis can obscure the responsible path.
Do not repeatedly reboot a machine affected by this result before collecting the dump and event logs. Recovery actions should follow the component identified by the stack and parameters, not merely the symbolic stop-code name.
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