How to fix Windows update error 0x800f0801?

Error 0x800f0801 means the Windows servicing stack could not start a session, so DISM or Windows Update stopped before doing anything. It is usually the second error: something else failed first. Restart the PC, run DISM again from an administrator window, and read CBS.log if it comes back.

Facts checked on 15 October 2026. Steps written for Windows 11 (25H2 and 26H2) and Windows 10 22H2.

What error 0x800f0801 means in DISM and Windows Update

0x800f0801 belongs to Component Based Servicing (CBS), the part of Windows that installs, changes and removes updates and features. Its name is CBS_E_NOT_INITIALIZED. A program such as DISM or Windows Update asked CBS to work in a servicing session, and that session had never been set up.

That is why the code tells you little by itself. In the logs it almost always sits next to another error that stopped the session first. One CBS.log quoted on Microsoft Q&A shows the exact line: Cannot GetSessionID on a session that has not been initialized. [HRESULT = 0x800f0801 - CBS_E_NOT_INITIALIZED].

The Windows Update page in the picture says: There were problems installing some updates, but we'll try again later. Under it is the failed update with the code. The message is the same for many update errors, so the code is what you search for.

Why error 0x800f0801 appears

The causes are ordered from the most likely to the least likely. Microsoft does not publish a list for this code, so the order comes from what the code means, from logs that users posted on Microsoft Q&A and from Microsoft's guide to update corruption.

In the Microsoft Q&A thread on a Windows 11 upgrade, the log showed 0x800f0801 when DISM checked the image health, and next to it a Spanish language feature package that failed with 0x800f0825 - CBS_E_CANNOT_UNINSTALL. The upgrade failed for months until that cause was dealt with.

How to fix error 0x800f0801

Fix 1 and Fix 2 are specific to this code and cost minutes. Fix 3 to Fix 5 are the general update repairs for a damaged store or cache. Fix 6 and Fix 7 are for version upgrades that keep failing. Use Restart, not Shut down, between fixes.

Fix 1. Restart the PC fully and run DISM or the update again as administrator

5 minutesNo riskEveryone, first. Especially when the PC has not restarted since the last update or Windows Update was busy while you ran DISM.

CBS opens one servicing session at a time and finishes pending work at restart. A restart clears a half-done operation, so the next DISM run or update can open a fresh session instead of failing with CBS_E_NOT_INITIALIZED.

1. Open Settings > Windows Update. If it says an update is installing or waiting for a restart, let it finish first.
2. Open Start, select the power button and select Restart, not Shut down.
3. After the restart, right-click Start and select Terminal (Admin). Select Yes when Windows asks for permission.
4. Close any other window that runs DISM or SFC. Run only one servicing command at a time.
5. Run the health check again:

   DISM /Online /Cleanup-Image /ScanHealth

6. If you saw the code in Windows Update, select Check for updates again instead.

Fix 2. Find the real error in CBS.log and dism.log

10 minutesNo riskFix 1 did not help. Always worth doing before a reinstall, because it tells you which fix to use.

0x800f0801 says only that the session did not start. Microsoft's guide to update corruption sends you to CBS.log for the details, and the line near 0x800f0801 names the package or file that broke the session.

1. Press Win + R, type %windir%\Logs\CBS and press Enter.
2. Copy CBS.log to the Desktop and open the copy in Notepad. Windows keeps the original open, so do not edit it.
3. Press Ctrl + F and search for 0x800f0801. Note the time of the last hit.
4. Search for Error around that time, above and below. Write down every other code and package name you find.
5. Do the same in %windir%\Logs\DISM\dism.log if the error came from DISM.

Fix 3. Repair the component store with DISM and SFC

15 to 40 minutesNo riskCBS.log or DISM points to a damaged component store, or you found nothing in the log.

Microsoft's first answer to update corruption is DISM with RestoreHealth, which downloads clean copies of damaged components from Windows Update, and then SFC. A repaired store lets CBS open its session again.

1. Open an elevated command window. Right-click Start and select Terminal (Admin), or type cmd in the search box, right-click Command Prompt and select Run as administrator. Select Yes when Windows asks for permission.

   

2. Run DISM first. Type the command below and press Enter. DISM downloads clean copies of damaged components from Windows Update, so it can take several minutes. Wait until it says The operation completed successfully.

   DISM.exe /Online /Cleanup-Image /RestoreHealth

   

3. Run System File Checker. In the same window, type the command below and press Enter. Do not close the window until the verification reaches 100%.

   sfc /scannow

   

4. Read the result and restart. Compare the last message with the table below this guide, then restart the PC so that repaired files are loaded.

   

These steps were written for Windows 11 24H2 and 25H2. The full page with the other versions and what each result means: Run DISM and SFC to repair Windows system files

If RestoreHealth fails because the PC cannot reach Windows Update, use a Windows ISO of the same version as the repair source. Microsoft gives the form DISM.exe /Online /Cleanup-Image /RestoreHealth /Source:<path>\windows /LimitAccess, where the source must run the same Windows version.

Fix 4. Reset the Windows Update components

10 minutesLow riskA monthly, .NET or feature update fails in Windows Update, and DISM itself now works.

A damaged download in the SoftwareDistribution folder is used again at every retry. Stopping the update services and renaming the cache folders makes Windows download and start the update from zero.

1. Open Command Prompt as administrator. Type cmd in the search box, right-click Command Prompt and select Run as administrator. Select Yes when Windows asks for permission.
2. Stop the update services. Type the commands below and press Enter after each one. If Windows says that other services depend on Cryptographic Services, it stops them too. A message that a service is not started is fine.

   net stop wuauserv
   net stop bits
   net stop cryptsvc

3. Delete the download queue files. This clears the list of downloads that the Background Intelligent Transfer Service keeps. If Windows says it cannot find the files, continue.

   del "%ALLUSERSPROFILE%\Application Data\Microsoft\Network\Downloader\qmgr*.dat"

4. Rename the update cache folders. Renaming keeps a copy in case you need it; Windows creates new, empty folders when the services start again. If you get Access is denied, a service is still running: repeat the previous step.

   ren %systemroot%\SoftwareDistribution SoftwareDistribution.old
   ren %systemroot%\System32\catroot2 catroot2.old

5. Start the services again. Type the commands below and press Enter after each one. The requested service has already been started is fine: Windows started it on its own.

   net start cryptsvc
   net start bits
   net start wuauserv

6. Restart and check for updates. Restart the PC. Then select Start > Settings > Windows Update > Check for updates. The first check can take longer than usual because everything is downloaded again.

These steps were written for Windows 11 and Windows 10 (the steps are the same). The full page with the other versions and what each result means: Reset Windows Update components

Fix 5. Install the failing update manually from the Microsoft Update Catalog

15 to 30 minutesLow riskOne cumulative or .NET update keeps failing, while DISM reports a healthy store.

The standalone installer starts its own servicing session with a fresh copy of the package, outside the Windows Update download.

1. Check your Windows version. Press Windows key + R, type winver and press Enter. Note the version (for example 25H2) and the OS build.
2. Find the KB number. Open Settings > Windows Update. A failed or pending update is listed with its KB number; earlier ones are under Update history.
3. Check the processor type. Open Settings > System > About and look at System type: an x64-based PC needs the x64 file, an ARM-based PC (for example Snapdragon) needs the arm64 file.
4. Search the catalog. Open the Microsoft Update Catalog at catalog.update.microsoft.com in your browser, type the KB number (for example KB5124010) in the search box and press Enter.
5. Pick the right row. Find the row whose title names your Windows version and your processor type (x64-based or arm64-based) and select Download on that row.
6. Download every file listed. A window lists one or more .msu links. Download all of them into one empty folder, for example C:\packages. On Windows 11 24H2 and later the list can include earlier checkpoint updates that the new one needs.
7. Install a single file. If there is only one file, double-click it and confirm the installation in the Windows Update Standalone Installer.
8. Install several files with DISM. If there are several files, open an elevated Terminal or Command Prompt and run DISM with the newest file. DISM finds the other files in the same folder and installs them in the right order.

   DISM /Online /Add-Package /PackagePath:C:\packages\<newest-file>.msu

9. Restart. Restart the PC when the installation finishes, then run winver again: the OS build should have changed.

These steps were written for Windows 11 24H2 and later; Windows 10 22H2. The full page with the other versions and what each result means: Install an update from the Microsoft Update Catalog

Fix 6. Upgrade from a clean boot

20 minutes plus the upgradeLow riskA feature update, Windows 11 Setup or the Installation Assistant fails with 0x800f0801, and monthly updates install fine.

A clean boot starts Windows with Microsoft services only. In the Microsoft Q&A thread, the advice that the asker accepted was a clean boot, removing a third-party security suite and updating the BIOS before the upgrade.

1. Open System Configuration. Select Search on the taskbar, type msconfig and select System Configuration from the results.
2. Hide Microsoft services. On the Services tab, select the Hide all Microsoft services check box. Only services from other companies stay in the list.
3. Disable the remaining services. Select Disable all, then select Apply.
4. Open Task Manager. On the Startup tab of System Configuration, select Open Task Manager.
5. Disable the startup apps. On the Startup apps tab in Task Manager, select each item whose status is Enabled and select Disable. Write down or take a screenshot of the items you disable: you need the list to turn them back on.
6. Confirm the changes. Close Task Manager. On the Startup tab of System Configuration, select OK.
7. Restart and test. Restart the PC. Windows now starts in a clean boot environment: try again the thing that failed (run the app, install the update, uninstall the program).

These steps were written for Windows 11 25H2 and 26H2. The full page with the other versions and what each result means: How to perform a clean boot in Windows

If you use a third-party security suite, pause it for this one upgrade only and turn it back on afterwards: Turn off Microsoft Defender protection for a moment. Check your PC maker's support page for a newer BIOS or UEFI firmware, since users report that an old one blocked the upgrade.

Fix 7. Reinstall Windows over itself and keep your apps and files

1 to 2 hoursRead the warningEvery update fails, DISM cannot repair the store, or a version upgrade fails after Fix 6.

A repair reinstall replaces the system files and the component store with a clean copy, so CBS starts from a healthy base. Apps, files and settings stay.

1. Open Recovery in Settings. Open Settings > System > Recovery. Next to Fix problems using Windows Update, select Reinstall now. This keeps your apps, files and settings.

   

2. Start the reinstall. Choose whether the PC may restart on its own 15 minutes after the installation, then select OK.
3. Wait and restart. Windows Update downloads and installs a repair copy of your current Windows version. Keep the PC plugged in and online, and restart it when asked.

These steps were written for Windows 11 22H2 and later. The full page with the other versions and what each result means: Reinstall Windows without losing files

If Fix problems using Windows Update is missing, download the Windows 11 ISO from Microsoft, open it, run setup.exe and keep the choice Keep personal files and apps. On Windows 10 22H2 use the Windows 10 media, and plan the move to Windows 11, since Windows 10 left support on 14 October 2025.

If error 0x800f0801 is still there

Before you reset Windows, collect what a support agent or administrator needs. It saves a round of questions.

• The full code and where you saw it: DISM, Update history or Windows Setup.
• The KB number of the failed update, from Settings > Windows Update > Update history.
• Your version and build: press Win + R, type winver and press Enter.
• Copies of C:\Windows\Logs\CBS\CBS.log and C:\Windows\Logs\DISM\dism.log.

How to keep error 0x800f0801 from coming back

Frequently asked questions

What does error 0x800f0801 mean?

It means CBS_E_NOT_INITIALIZED: the Windows servicing stack was asked to work in a session that had never been set up. DISM, Windows Update and Windows Setup all use this stack, so all three can show the code. It is almost always the result of an earlier failure, such as a pending operation, a broken language pack or a damaged component store. Restart the PC first, then read CBS.log to find that earlier failure.

How do I fix DISM error 0x800f0801?

Restart the PC with Restart, not Shut down, and make sure Windows Update is not installing anything. Then open Terminal (Admin) and run DISM /Online /Cleanup-Image /ScanHealth again, with no other DISM or SFC window open. If DISM still stops with Error: 0x800f0801, open C:\Windows\Logs\DISM\dism.log and CBS.log and look for the other error near it. A store corruption code means DISM RestoreHealth with a matching Windows ISO as the source.

Is 0x800f0801 the same as CBS_E_NOT_APPLICABLE?

No. Several old pages, ours included, gave that name, but CBS_E_NOT_APPLICABLE is 0x800f081e, which means an update package does not fit your Windows edition, version or processor type. 0x800f0801 is CBS_E_NOT_INITIALIZED, as the HRESULT lines in CBS.log show. The difference matters: a not applicable update needs the right file, while 0x800f0801 needs the cause that stopped the servicing session.

Why does a Windows feature update fail with 0x800f0801?

During a version upgrade, Setup checks the health of the current Windows before it continues. If that check cannot open a servicing session, the upgrade stops with 0x800f0801. Reports on Microsoft Q&A tie it to language packs that cannot be changed, to third-party security suites and to old firmware. Read CBS.log first, then try the upgrade from a clean boot, and use the repair reinstall from an ISO if it still fails.

Will SFC /scannow fix 0x800f0801?

Only when the cause is a damaged system file. SFC repairs protected Windows files, while 0x800f0801 usually comes from the component store or from a package that failed. Run DISM RestoreHealth first, as Microsoft recommends for update corruption, and SFC after it. If both finish without errors and the update still fails, the cause is in the update cache or in a package named in CBS.log.

Can turning off my antivirus fix error 0x800f0801?

Not as a lasting fix. No Microsoft source ties this code to security software. Users report that removing a third-party suite helped one version upgrade, so pausing it for one upgrade attempt is a fair test. Turn it back on right after, whatever the result. Microsoft Defender does not need to be turned off for updates.

Do I lose files when I fix 0x800f0801?

No, with Fix 1 to Fix 6 nothing personal is touched. They restart services, repair system files or install updates. The repair reinstall in Fix 7 keeps apps, files and settings when you choose Keep personal files and apps, but any reinstall can fail, so back up first. Only Reset this PC removes installed apps, and with Keep my files your documents stay.

Is 0x800f0801 related to error 0x800f8011?

No, they are different codes that some searches mix up. 0x800f8011 is a separate Windows Update error with its own causes, and we explain it in our guide to error 0x800f8011. This page is about 0x800f0801, the servicing session that did not start. If you see both codes, fix the one in Update history first and read CBS.log for the other.

Does 0x800f0801 still appear on Windows 10?

Yes, the code exists on Windows 10 and Windows 11 and the fixes are the same. Windows 10 left support on 14 October 2025, so a Windows 10 22H2 PC receives security updates only through Extended Security Updates. If DISM or the update fails there, repair it with the same steps, then plan the move to Windows 11 if your PC supports it.