I like to keep my Windows `11 computers fully patched. The 0x800f0922 error with Windows 11’s 2025-12 and 2026-01 Security Updates blocked me. That error caused the update to be rolled back. Windows Update kept presenting this update, which caused repetitive, lengthy reboot cycles that only ended with failure.
The fix is easy.
Mitigating root cause
It turns out root cause was discernible by searching C:\Windows\Logs\CBS\CBS.log for the first error. This log apparently contains errors encountered during updates.
I searched on , error (comma, then space, then error) to find errors. It’s likely best to focus on the first error as that should be what triggers a rollback. In my case, the first error was vague, but I found the root cause on the second error, which appeared just a few lines later.
The error included HRESULT_FROM_WIN32(ERROR_DISK_FULL). Trivial searching landed me on a theory that my boot partition was full.
Windows users are used to the C drive being the main drive you see. This C drive is actually a partition of your drive. Typically, a partition a portion of a drive that is accessed using a drive letter.
Customarily, the C partition includes nearly all your drive. If you have a 500 GB hard drive, then your C partition should be close to 500 GB.
There are also small, hidden partitions. Without special tricks, you can’t see them. In my case, I have a 0.1 GB boot partition. This boot partition is accessed by your computer when you first turn it on. The initial loading screens are really your computer running software in this tiny boot partition, until it passes control on to Windows on the C drive.
My boot partition was nearly full. It had so little free space, the updater couldn’t add some files to it. Hence the disk-full error!
The easy fix
Fixing this is easy, described in a Microsoft support article, where you simply delete some files from the boot partition that are unlikely to ever be used. While the article only contained Windows 10 steps, they worked for Windows 11. The steps:
- Open Command Prompt in administrator mode. (In your taskbar’s search box, search for
command prompt. When the Command Prompt icon displays, right-click on it, select Run as administrator, and hit Yes on the confirmation dialog.) - In the Command Prompt window, type these commands:
mountvol y: /scd EFI\Microsoft\Boot\Fonts- (do not do this unless the prior steps had no errors)
del *.*
Now your boot partition has enough space. Go back to Windows Update and attempt the security update again. It should work.