Microsoft: KB5021233 causes blue screens with 0xc000021a errors

Microsoft is investigating a known issue leading to Blue Screen of Death (BSOD) crashes with 0xc000021a errors after installing the Windows 10 KB5021233 cumulative update released during this month’s Patch Tuesday.

The company warned over the weekend that “after installing KB5021233, some Windows devices might start up to an error (0xc000021a) with a blue screen.”

This known issue is likely caused by a mismatch between the file versions of hidparse.sys in system32 and system32/drivers in the Windows folder, “which might cause signature validation to fail when cleanup occurs.”

The list of affected platforms includes only client Windows 10 versions, from Windows 10 20H2 to the latest release, Windows 10 22H2.

Redmond added that it’s already working on a fix to address this newly acknowledged issue but hasn’t yet shared when it will be available.

Workaround for affected Windows 10 systems

However, the company did share a temporary solution to workaround the blue screen issue and revive the affected systems to start as expected.

This requires users to copy the hidparse.sys file from the system32 folder into system32drivers via the Windows Recovery Environment (WinRE) so that the signature validation no longer fails during cleanup.

To mitigate this issue on impacted devices, you need to go through the following steps:

You will need to enter Windows Recovery Environment. If your device has not automatically started up into WinRE, please see Entry points into WinRE.
Select the Troubleshoot button.
Select the “Start recovery, troubleshooting, and diagnostic tools” button.
Select the “Advanced Options” button.
Select the “Command Prompt” button and wait for your device to restart, if needed.
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.
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:windowssystem32drivershidparse.sys C:windowssystem32hidparse.sys
Once the previous command completes, type: exit
Select the “Continue” button.
Windows should now start up as expected.

“It is not recommended to follow any other workaround than those recommended above. We do not recommend deleting the hidparse.sys from your WindowsSystem32 folder,” Microsoft added.

Redmond is also investigating a known issue linked to this month’s Windows Server Patch Tuesday updates that triggers errors when creating new virtual machines on some Hyper-V hosts.