Security News > 2022 > December > Microsoft: KB5021233 causes blue screens with 0xc000021a errors
Microsoft is investigating a known issue leading to Blue Screen of Death 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 with a blue screen."
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.
Sys file from the system32 folder into system32drivers via the Windows Recovery Environment so that the signature validation no longer fails during cleanup.
Your device should restart to a Command Prompt window.
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.