Windows 11: Update KB5021255 / KB5021234 cannot be installed

Windows[German]There are reports from Windows 11 users about issues installing Dec. 13, 2022 security updates KB5021255 (Windows 11 22H2) or KB5021234 (Windows 11 21H2). A German blog reader has contacted me because in his company all Windows 11 clients refuse update installation. But there are also references on the web, where the problem is also addressed.


Update KB5021255 for Windows 11 22H2

Cumulative Update KB5021255 was released on December 13, 2022 for Windows 11 22H2. The same was for KB5021234 (Windows 11 21H2) – see Patchday: Windows 11/Server 2022-Updates (December 13, 2022)). Beside the fixes mentioned within the blog post Windows 11 22H2: December 2022 update (12/13/2022) fixes Task Manager display issues the updates shall fix some unnamed vulnerabilities. A list of bug fixes can be found in the blog post Windows 11 22H2: Preview Update KB5020044 (Nov. 29, 2022).

Install issues with updates KB5021255/KB5021234

German blog reader Timo H. already contacted me by mail on December 27, 2022 and asked if I was aware of installation problems in connection with security update KB5021255. I had to deny ad hoc, but Timo writes that this update cannot be installed on all clients in his company environment.

Timo pointed me to the blog post Windows 11 KB5021255 & KB5021234: Major issues reported in December 2022 update from Windows Latest, which addresses major issues related to this update. Windows Latest has user messages reporting installation issues. However, the affected users are often not shown a truly informative error message that provides clues as to the reason for the installation problem.

Some users at least get the update error 0x800f081f displayed before the installation aborts. I had addressed the error code in the blog post Windows 10 V1909: Update KB4528760 drops error 0x800F081F. However, it often doesn't help. Sometimes the installation starts, but the process fails halfway and the OS reverts to the previous build with no meaningful errors reported.

WinCentral also describes installation errors in this article and mentions reports that PCs with AMD CPU randomly freeze during operation after the update installation. Installation crashes are also mentioned there.


Some users also report a broken Start menu, involving StartMenuExperienceHost.exe. I had mentioned this in my German comment here and linked to this thread at Is somebody affected by the installation or other issues? If so, is there a known cause or fix?

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