How to Fix Windows 11 Update Error 0x800f0983 (KB5066835 – October 2025 Cumulative Update)

If your Windows 11 25H2 update keeps failing with error code 0x800f0983, you’re not the only one. Many users are reporting installation errors while trying to install the October 2025 Cumulative Update (KB5066835, build 26200.6899).

What Causes Error 0x800f0983?

The error 0x800f0983 occurs when Windows Update fails to process system components correctly.
Common causes include:

• Corrupted update cache or servicing stack
• Missing or damaged system files
• Incomplete installation of previous cumulative updates
• Outdated Servicing Stack Update (SSU)
• Third-party antivirus or VPN interference

Step-by-Step Fix for KB5066835 Installation Failure

Follow these methods in order for the best chance of success:

1. Run the Windows Update Troubleshooter

1. Go to Settings → System → Troubleshoot → Other troubleshooters
2. Find Windows Update → Click Run
3. Let Windows detect and fix update-related problems
4. Restart your PC and check for updates again

2. Reset Windows Update Components

This will clear out old update data and rebuild new ones.
Open Command Prompt as Administrator and type each line:

net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver
ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
ren C:\Windows\System32\catroot2 catroot2.old
net start wuauserv
net start cryptSvc
net start bits
net start msiserver

Then go back to Settings → Windows Update → Retry all.

3. Repair System Files Using DISM and SFC

If system files are corrupted, this step will fix them.

Run the following commands in Command Prompt (Admin):

DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow

Wait for both to complete (this can take 15–20 minutes).

Restart and retry the update.

4. Manually Install KB5066835

If the automatic update keeps failing:

1. Go to the official Microsoft Update Catalog
2. Search for KB5066835
3. Download the x64 version for your system
4. Double-click the .msu file to install manually

5. Clean Up Old Components

Old or pending update data may block new ones.
Run this command:

DISM /Online /Cleanup-Image /StartComponentCleanup

Once done, restart your PC.

6. Check for the Latest Servicing Stack Update (SSU)

Before installing KB5066835, make sure you have the latest SSU:

• Open Settings → Windows Update → Update History
• Scroll to Servicing Stack Updates
• If none appear for October 2025, install the latest one manually from the Microsoft Update Catalog

7. Use Windows 11 Installation Assistant (Optional)

If nothing else works:

1. Visit the Windows 11 Software Download Page
2. Download Installation Assistant
3. Run it and follow on-screen steps to upgrade without losing files

8. Advanced: In-place Repair Upgrade

For persistent cases:

1. Download the official Windows 11 ISO (25H2)
2. Mount it and run setup.exe
3. Choose Keep personal files and apps
4. This refreshes your system and fixes update-related corruption

After Fixing

Go to Settings → Windows Update → Update history

You should now see: “2025-10 Cumulative Update for Windows 11, version 25H2 (KB5066835) – Successfully installed.”

Error 0x800f0983 is common in cumulative updates like KB5066835, and it’s fixable with cleanup, repair, or manual installation. If you’re stuck, the DISM + manual update combo almost always resolves it.

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