Microsoft confirms KB5021233 update is causing 0xc000021a errors and blue screens in Windows 10

The curse of the problematic Windows update strikes again! Following the release of the KB5021233 update for Windows 10 last week, Microsoft has acknowledged that the cumulative security update is causing blue screens for some users.

The company is now investigating the cause the issue that leads to a BSoD (Blue Screen of Death) and a 0xc000021a error. The problem affects Windows 10 versions 20H2, 21H1, 21H2 and 22H2, and Microsoft has a workaround for users to try until a fix is developed.

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The problem stems from a potential mismatch between the file versions of hidparse.sys in c:\windows\system32 and c:\windows\system32\drivers. Microsoft explains that this might cause signature validation to fail when cleanup occurs following the installation of the KB5021233 update.

Pointing out that it is a bad idea to simply go ahead and delete the hidparse.sys files from your Windows\System32 folder, Microsoft offers up the following workaround using the Windows Recovery Environment (WinRE):

1. ​You will need to enter Windows Recovery Environment. If your device has not automatically started up into WinRE, please see Entry points into WinRE.
2. ​Select the Troubleshoot button.
3. ​Select the "Start recovery, troubleshooting, and diagnostic tools" button.
4. ​Select the "Advanced Options" button.
5. ​Select the "Command Prompt" button and wait for your device to restart, if needed.
6. ​Your device should restart to a Command Prompt window. You might need to sign into your device with your password before getting to the Command Prompt window.
7. ​Run the following command (Important: If Windows is not installed to C:\windows you will need to modify the command to your environment): xcopy C:\windows\system32\drivers\hidparse.sys C:\windows\\system32\hidparse.sys
8. ​Once the previous command completes, type: exit
9. ​Select the "Continue" button.
10. ​Windows should now start up as expected.

While failing to suggest a timeframe, Microsoft says that it is working on a resolution and will provide an update in an upcoming release.

Image credit: AndreyPopov / depositphotos