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0xC000021AApplicationCritical

Error 0xC000021A — STATUS_SYSTEM_PROCESS_TERMINATED | Application Error Fix

Windows 10Windows 11Windows Server 2016Windows Server 2019Windows Server 2022

What Does 0xC000021A Mean?

A critical system process (csrss.exe or winlogon.exe) terminated unexpectedly. Because these processes are essential, the system can no longer function and must stop.

Real-World Causes

  1. 1Corrupted system files critical to Windows operation
  2. 2Incompatible or corrupted third-party driver or service
  3. 3Failed Windows Update that corrupted system processes
  4. 4Malware that damaged or replaced critical system executables
  5. 5Mismatched system DLLs after a partial update or restore

Symptoms

  • ⚠BSOD with STOP code 0xC000021A
  • ⚠Windows fails to boot and shows blue screen
  • ⚠System enters boot loop with repeated BSOD
  • ⚠Error appears after installing a driver or Windows Update

DIY Fix

Beginner-friendly steps you can try at home

  1. 1Boot into Safe Mode (hold Shift during restart > Troubleshoot > Startup Settings)
  2. 2Use System Restore to revert to a point before the error
  3. 3If a driver was recently installed, uninstall it from Safe Mode
  4. 4Uninstall the most recent Windows Update from recovery environment

Advanced Fix

For experienced users and IT professionals

  1. 1From Recovery Command Prompt: sfc /scannow /offbootdir=C:\ /offwindir=C:\Windows
  2. 2Run DISM offline: DISM /Image:C:\ /Cleanup-Image /RestoreHealth
  3. 3Replace corrupted system files manually from installation media
  4. 4Perform an in-place upgrade (repair install) from Windows installation media
  5. 5Analyze the minidump in C:\Windows\Minidump with WinDbg to identify the faulting component

Frequently Asked Questions

Is this a virus?
Not necessarily, but malware can cause this by corrupting critical system files. After fixing the boot issue, run a full antivirus scan. If you suspect malware, scan with Windows Defender Offline from the recovery environment.
What are csrss.exe and winlogon.exe?
These are essential Windows system processes. csrss.exe (Client/Server Runtime) manages console windows and thread creation. winlogon.exe handles user login, logout, and the Ctrl+Alt+Del screen. If either crashes, Windows cannot continue.

Related Error Codes

0xC0000225STATUS_NOT_FOUND0xC0000005STATUS_ACCESS_VIOLATION0xC0000142STATUS_DLL_INIT_FAILED

About the Author

Windows Troubleshooting Team

Verified against official Microsoft documentation and real-world diagnostic data. Error behavior confirmed across Windows 10, Windows 11, and Windows Server.