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Windows Update error 0x800f0922: what it means and how to fix it

Short answer

Error 0x800f0922 (CBS_E_INSTALLERS_FAILED) means Windows downloaded an update but could not finish installing it, so it rolled the changes back. On Windows 11 24H2 and 25H2 in 2026 the usual cause is a nearly full EFI System Partition. First turn off any VPN, restart, and check for updates again so you get the fixed cumulative update.

What this message means

0x800f0922 is a Component-Based Servicing error named CBS_E_INSTALLERS_FAILED. The update downloads fine, but one of the installer steps that runs during the restart fails. Windows then shows "Something didn't go as planned. Undoing changes" or "We couldn't complete the updates" and returns you to the previous build. The code does not name one fault. It is a catch-all for a failed install phase. Common triggers are too little free space on the small hidden EFI System Partition (ESP), a VPN blocking the connection to Windows Update, a damaged component store, a .NET Framework 3.5 component that will not install, or a corrupted scheduled task. Your files are not affected by the rollback.

Common causes

CauseHow to tell
EFI System Partition (ESP) is nearly full. This is the known issue with the May 2026 update KB5089549 on Windows 11 24H2/25H2.The update gets to about 35 to 36% during the restart, then shows "Something didn't go as planned. Undoing changes." The ESP has 10 MB or less free. This is common on PCs with a 100 MB ESP or where a dual-boot or OEM tool stored files there.
A VPN or proxy is blocking the connection to Microsoft's update servers.A VPN client is connected (work VPN, NordVPN, and so on) when the update runs. The same update installs as soon as you disconnect.
Not enough free space on the C: drive.Settings > System > Storage shows only a few GB free. Microsoft recommends at least 20 GB free on 64-bit Windows for updates.
Corrupt system files or a damaged component store (WinSxS).Several different updates fail with the same code, or DISM /RestoreHealth reports corruption. C:\Windows\Logs\CBS\CBS.log shows errors just before the line "HRESULT = 0x800f0922 - CBS_E_INSTALLERS_FAILED".
.NET Framework 3.5 fails to install as part of the update.The failed item in Update history is a .NET Framework update, or turning on .NET Framework 3.5 under Windows Features also fails with 0x800f0922.
A corrupted scheduled task (SecureBootEncodeUEFI) or wrong permissions on the licensing folder. This is mostly seen on Windows Server.CBS.log shows "Installer name: 'Task Scheduler'" with "RegisterTask failed 0x80070002", and Event Viewer > Microsoft-Windows-TaskScheduler/Operational shows Event ID 146 for \Microsoft\Windows\PI\SecureBootEncodeUEFI.

How to fix it

1. Disconnect the VPN, restart, and install the newest cumulative update

  1. Disconnect any VPN and quit the VPN app completely (right-click its tray icon and choose Quit/Exit).
  2. Restart the PC. A normal restart, not Shut down.
  3. Open Settings > Windows Update (Windows 11) or Settings > Update & Security > Windows Update (Windows 10) and select Check for updates.
  4. On Windows 11 24H2/25H2, if KB5089549 keeps failing, install KB5089573 (May 26, 2026) or any later cumulative update. Microsoft says that update addresses the EFI partition failure.
  5. If the later update is listed under "Optional updates", open Advanced options > Optional updates, tick it and select Download & install.

2. Run the Windows Update troubleshooter

Windows 11 and Windows 10 (menu paths differ)

  1. Windows 11: Start > Settings > System > Troubleshoot > Other troubleshooters, then select Run next to Windows Update.
  2. Windows 10: Start > Settings > Update & Security > Troubleshoot > Additional troubleshooters > Windows Update > Run the troubleshooter.
  3. Apply any fixes it offers, restart, then check for updates again.

3. Free up space on the EFI System Partition

UEFI PCs, mainly Windows 11 24H2/25H2. Needs an administrator account.

  1. Right-click Start and open Terminal (Admin) or Command Prompt (Admin).
  2. Type mountvol S: /s and press Enter. This gives the hidden EFI partition the drive letter S:. If S: is already in use, pick another unused letter.
  3. Type fsutil volume diskfree S: and press Enter to see the free space. If it shows about 10 MB or less, continue.
  4. Delete the unused boot font files: del S:\EFI\Microsoft\Boot\Fonts\*.* then press Y to confirm. These fonts are only used to draw boot-menu text, and this frees roughly 10 to 15 MB. Do not delete anything else on S:.
  5. Type mountvol S: /d to remove the drive letter again, restart, and retry the update.
  6. If the partition is still nearly full (common with a 100 MB ESP), the permanent fix is to enlarge it to 200 to 300 MB with a partition tool. Back up the PC first.

4. Free up space on C: and repair system files with DISM and SFC

  1. Open Settings > System > Storage and use Cleanup recommendations or Temporary files until at least 20 GB is free.
  2. Open Command Prompt as administrator.
  3. Run DISM.exe /Online /Cleanup-image /Restorehealth and wait for it to reach 100%. It can pause at 20% or 62% for several minutes.
  4. Run sfc /scannow.
  5. Restart and check for updates again.

5. Turn on .NET Framework 3.5 manually

When the failing item is a .NET Framework update

  1. Press Windows key + R, type optionalfeatures and press Enter.
  2. Tick .NET Framework 3.5 (includes .NET 2.0 and 3.0) and select OK.
  3. Choose Let Windows Update download the files for you, and keep the VPN off while it runs.
  4. Restart, then run Windows Update again.

6. Reinstall Windows without losing files

Windows 11 (Recovery option) and Windows 10 (Media Creation Tool)

  1. Windows 11: Settings > System > Recovery > Fix problems using Windows Update > Reinstall now. This reinstalls your current version and keeps apps, files and settings.
  2. Windows 10: download the Media Creation Tool from Microsoft's Windows 10 download page, run it, choose Upgrade this PC now, and keep personal files and apps.
  3. After it finishes, run Windows Update again to install the pending updates.

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Still not fixed?

Open C:\Windows\Logs\CBS\CBS.log, search for 0x800f0922, and read the error lines just above it. They name the step that failed (for example 'Task Scheduler', a .NET package, or a licensing file). If it mentions the SecureBootEncodeUEFI task, follow Microsoft Learn's article on 0x800F0922, which covers removing staged packages and the corrupted task's registry entries. If CBS.log mentions licensing tokens, give the Users and NETWORK SERVICE accounts write permission on C:\Windows\System32\spp. On a work or school PC, contact IT, because VPN, proxy or update policy is often the cause. For home PCs, Microsoft Support can take the CBS.log and a TSS data collection if nothing here works.

Questions people ask

Is it safe to ignore error 0x800f0922?

Your PC keeps working on the previous build, so nothing is broken right away. But you will not get that month's security fixes until the update installs, so fix it soon.

Why does the update stop at 35% and say 'Undoing changes'?

On Windows 11 24H2 and 25H2 this is the known KB5089549 issue. The EFI System Partition is too full to stage new boot files. Install KB5089573 or a later update, or free space on the EFI partition.

Will deleting the boot fonts on the EFI partition stop Windows from starting?

No. The files in \EFI\Microsoft\Boot\Fonts only control how boot-menu and recovery text is drawn, and Windows starts normally without them. Delete only that folder's contents and nothing else on the partition.

Does a VPN really cause 0x800f0922?

Yes. Microsoft's own troubleshooting page lists disabling an active VPN as a fix for this code, because the VPN can block the connection to update servers during install.

Will I lose files fixing this error?

None of the fixes above delete personal files. Even 'Fix problems using Windows Update' and a Media Creation Tool in-place upgrade keep your files and apps. Still, back up before changing partitions.

Sources

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