Fixes / Windows · Checked

Windows Update error 0x800f081f: what it means and how to fix it

Short answer

Error 0x800f081f (CBS_E_SOURCE_MISSING) means Windows could not find the source files it needed to install an update or feature, usually because its component store is damaged. Run DISM /Online /Cleanup-Image /RestoreHealth and then sfc /scannow in an administrator Command Prompt, restart, and try the update again. If DISM fails with the same code, point it at a Windows ISO.

What this message means

0x800F081F is a Component-Based Servicing code named CBS_E_SOURCE_MISSING. Its official text is "The source files could not be found." Windows keeps copies of system components in a store under C:\Windows\WinSxS and uses them to apply cumulative updates and to add optional features such as .NET Framework 3.5. If a file Windows needs is missing or corrupt, and it can't download a good copy from Windows Update or an alternate source you gave it, the install stops with this code. You see it in Settings > Windows Update as "Install error - 0x800f081f" and also from DISM or the Windows Features dialog.

Common causes

CauseHow to tell
Corrupted component store (WinSxS), often left behind by an earlier update that failed or was interruptedOne particular cumulative update (KBxxxxxxx) keeps failing with 0x800f081f while other updates install. Dism /Online /Cleanup-Image /ScanHealth reports "The component store is repairable."
Damaged Windows Update cache (SoftwareDistribution or catroot2 folders)The update downloads to 100%, fails at the install stage, and fails again at the same point on every retry, even after a restart.
Installing .NET Framework 3.5 (NetFx3) when Windows can't get the payloadThe error comes up while you enable .NET Framework 3.5 in Windows Features, or when an older app or game asks for it. DISM reports "The source files could not be found."
Wrong or unreadable alternate source given to DISM or set in Group PolicyYou ran DISM with /Source, or IT set "Specify settings for optional component installation and component repair". The path doesn't contain a sources\sxs folder or install.wim/install.esd, the ISO is for a different Windows version or edition, or your account can't read that location.
Work PC managed through WSUS or policy that blocks direct downloads from Windows UpdateSettings shows "Some settings are managed by your organization". Repairs work on home PCs but fail on this one. 0x800F0907 can show up alongside 0x800f081f.

How to fix it

1. Repair Windows with DISM and SFC

  1. Click Start, type cmd, right-click Command Prompt and choose Run as administrator.
  2. Run: DISM /Online /Cleanup-Image /RestoreHealth (it can take 10 to 30 minutes and may appear stuck at 62.3%, so let it finish).
  3. When it reports "The restore operation completed successfully", run: sfc /scannow and wait until it reaches 100%.
  4. Restart the PC.
  5. Go back to Windows Update and click Check for updates or Retry. If DISM itself failed with 0x800f081f, use the "Repair from a Windows ISO" fix below.

2. Reset the Windows Update cache

  1. Open Command Prompt as administrator.
  2. Stop the update services by running each line: net stop wuauserv, then net stop cryptSvc, then net stop bits, then net stop msiserver.
  3. Rename the caches: ren C:\Windows\SoftwareDistribution SoftwareDistribution.old and then ren C:\Windows\System32\catroot2 catroot2.old
  4. Start the services again: net start wuauserv, net start cryptSvc, net start bits, net start msiserver.
  5. Restart the PC and check for updates. The first scan takes longer while the cache rebuilds.

3. Run the Windows Update troubleshooter

Windows 11: Settings > System > Troubleshoot > Other troubleshooters. Windows 10: Settings > Update & Security > Troubleshoot > Additional troubleshooters.

  1. Open Settings with Windows key + I.
  2. Windows 11: go to System > Troubleshoot > Other troubleshooters and click Run next to Windows Update. Windows 10: go to Update & Security > Troubleshoot > Additional troubleshooters > Windows Update > Run the troubleshooter.
  3. Apply any fixes it suggests. It may open the Get Help app to run them.
  4. Restart and retry the update.

4. Repair from a Windows ISO when DISM can't find source files

  1. Download the ISO for the same Windows version, language and 32/64-bit type you have from microsoft.com/software-download (use the Media Creation Tool for Windows 10). Check your version with winver.
  2. Right-click the ISO and choose Mount. Note its drive letter, for example D:.
  3. In an administrator Command Prompt, list the editions: DISM /Get-WimInfo /WimFile:D:\sources\install.wim (use install.esd if that is the file in the folder). Note the index number of your edition, such as Windows 11 Pro.
  4. Run: DISM /Online /Cleanup-Image /RestoreHealth /Source:wim:D:\sources\install.wim:6 /LimitAccess and replace 6 with your index. For an .esd file, use /Source:esd:D:\sources\install.esd:6 instead.
  5. Run sfc /scannow, restart, and install the update again.

5. Install .NET Framework 3.5 from installation media

Only if the error appears while enabling .NET Framework 3.5

  1. First try it the normal way while connected to the internet: press Windows key + R, type optionalfeatures, tick .NET Framework 3.5 (includes .NET 2.0 and 3.0), and click OK.
  2. If that fails, mount a Windows ISO that matches your version and note its drive letter.
  3. In an administrator Command Prompt, run: Dism /online /enable-feature /featurename:NetFx3 /All /Source:D:\sources\sxs /LimitAccess (replace D: with your drive letter).
  4. On a managed PC, ask IT to enable "Specify settings for optional component installation and component repair" (Computer Configuration > Administrative Templates > System) and tick "Download repair content and optional features directly from Windows Update instead of Windows Server Update Services (WSUS)" or set an Alternate source file path. Then run gpupdate /force.

6. Reinstall Windows in place, keeping files and apps

Windows 11 (23H2 and later) has a built-in button. On Windows 10, use the Media Creation Tool.

  1. Back up important files first.
  2. Windows 11: go to Settings > System > Recovery, then under "Fix problems using Windows Update" click Reinstall now. Your apps, files and settings are kept.
  3. Windows 10, or if that button is missing: mount a matching ISO, run setup.exe, and choose "Keep personal files and apps".
  4. Leave at least 20 GB of free space on C: for the reinstall.
  5. When it finishes, open Windows Update. The pending updates normally install without the error.

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Still not fixed?

Open C:\Windows\Logs\CBS\CBS.log (or C:\Windows\Logs\DISM\dism.log) and search for "0x800f081f" or "Source missing". The lines around it name the exact package or file that is missing, which tells you which update or feature to target. You can also download the failing KB as a standalone .msu from the Microsoft Update Catalog and install it by double-clicking it. On a work or school PC, contact IT, because WSUS or Intune policies usually decide where repair files come from. If a clean in-place reinstall still fails, contact Microsoft Support through the Get Help app.

Questions people ask

What does error code 0x800f081f mean?

It is CBS_E_SOURCE_MISSING: Windows couldn't find the source files needed to install an update or feature. In almost all cases the local component store is damaged, or the repair source it was given is wrong.

Why does DISM RestoreHealth also fail with 0x800f081f?

DISM normally downloads replacement files from Windows Update, and it fails if the files it needs aren't available there. Mount a Windows ISO for the same version and point DISM at it with /Source:wim:D:\sources\install.wim:<index> /LimitAccess.

Is 0x800f081f related to .NET Framework 3.5?

It can be. Microsoft documents it as one of three common .NET Framework 3.5 install errors, together with 0x800F0906 and 0x800F0907. If it appears on a cumulative update instead, .NET 3.5 usually has nothing to do with it and component store repair is the fix.

Will Reinstall now delete my files?

No. The Windows 11 "Fix problems using Windows Update" option reinstalls the current Windows version and keeps your apps, files and settings. A backup beforehand is still sensible.

Can I just skip the update?

You can pause updates for a while, but the next cumulative update usually fails the same way until the corruption is repaired, and you miss the security fixes meanwhile.

Sources

Related errors