Windows 11 Update KB5124008 Stuck at 0%? How to Fix It

KB5124008 usually stalls because of a corrupted Windows Update cache, a stuck Background Intelligent Transfer Service (BITS) job, or not enough free space on your system drive. Restarting the update services and clearing the SoftwareDistribution folder fixes it in most cases. If it does not, installing the update manually from the Microsoft Update Catalog gets around the stuck progress bar entirely.

KB5124008 is the September 8, 2026 cumulative update for Windows 11, version 24H2 and 25H2. It moves your build number to 26100.9445 or 26200.9445, depending on which version you run. Alongside the usual security patches, it fixes the Teams and Outlook launch failures on Arm64 PCs, a problem KB5121003 caused last month, plus the mouse cursor and black wallpaper bug from KB5120998.

It's frustrating when the update fixing two known bugs gets stuck on its own installer. Here's how to get it moving.

How Do You Know If KB5124008 Is Truly Stuck?

Check the elapsed time first. If Settings > Windows Update shows "Downloading update 26%" and the percentage hasn't moved in more than 20 minutes, it's stuck, not slow.

Windows Update sometimes sits at a fixed number for a while during the "Working on updates" phase, especially on mechanical hard drives or systems with fewer than 8 GB of RAM. Give it 30 minutes before you assume something is wrong. If you restart your PC and it boots straight back to the desktop with no "Working on updates" screen, or Settings still shows the same stuck percentage after a fresh reboot, treat it as a genuine failure and move to the fixes below.

How Do You Fix KB5124008 Stuck at 0%?

Restart the Windows Update and BITS services through the Services app, then retry the update. This clears whatever hung process was blocking the download and resolves the 0% freeze for most people.

Here's the exact sequence:

• Press Windows key + R, type services.msc, and press Enter.
• Find Windows Update in the list, right-click it, and select Stop.
• Find Background Intelligent Transfer Service, right-click it, and select Stop.
• Find Cryptographic Services, right-click it, and select Stop.
• Open File Explorer and go to C:\Windows\SoftwareDistribution.
• Delete everything inside the Download subfolder (not the whole SoftwareDistribution folder). This clears the corrupted update files without touching your update history.
• Go back to Services, and start Windows Update, BITS, and Cryptographic Services again, in the same order.
• Open Settings > Windows Update and select Check for updates.

KB5124008 should now download from scratch instead of picking up the broken partial download.

What If Restarting Services Doesn't Fix It?

Run the Windows Update Troubleshooter and the DISM repair commands. Together they catch corruption a service restart alone misses, including a damaged component store.

Run these in order:

• Open Settings > System > Troubleshoot > Other troubleshooters, and run Windows Update.
• Open Command Prompt as administrator and run:

  DISM /Online /Cleanup-Image /RestoreHealth
  

• Wait for it to finish, then run:

  sfc /scannow
  

• Restart your PC and check for updates again.

The DISM command pulls clean system files from Windows Update itself, so it needs an internet connection to work. If DISM reports an error like 0x800f081f, your local update cache is too damaged for it to find a source, and you need the offline fix below.

How Do You Install KB5124008 Manually?

Download the standalone .msu file from the Microsoft Update Catalog and install it directly. This skips the Windows Update pipeline entirely, so a stuck download or corrupted cache no longer matters.

• Go to catalog.update.microsoft.com and search for KB5124008.
• Pick the download matching your Windows version: 24H2/25H2 for most PCs, or the Arm64 build if you run a Surface Pro X, Surface Pro 11, or another Arm-based PC.
• Download the .msu file.
• Double-click it and follow the installer prompts.
• Restart when it asks you to.

This method also works if Windows Update shows error 0x80070002 or 0x8024402f, both of which point to a broken connection between your PC and Microsoft's update servers rather than a problem with the update file.

Does KB5124008 Need More Free Disk Space Than Usual?

Yes. Cumulative updates for 24H2 and 25H2 need at least 20 GB of free space on your system drive to stage the update files before installation. Less than 20 GB free, and the download stalls without a clear error message.

Check your free space:

• Open File Explorer and click This PC.
• Right-click your C: drive and select Properties to see free space.

If you're under 20 GB, free up space before trying again:

• Open Settings > System > Storage and run Temporary files cleanup.
• Uninstall apps you don't use from Settings > Apps > Installed apps.
• Empty the Recycle Bin.

Once you clear enough room, retry the update. Low disk space is one of the most common causes of a KB5124008 install sitting there with no error at all.

Is a Third-Party Antivirus Blocking the Update?

It's possible, though less common than the causes above. Some antivirus tools flag the Windows Update installer's temporary files as suspicious and quarantine them mid-download, which leaves the progress bar frozen.

Temporarily disable real-time protection in your antivirus software, run Windows Update again, and re-enable protection once the update finishes. If the update completes successfully with protection off, add an exclusion for C:\Windows\SoftwareDistribution in your antivirus settings so this doesn't happen with every future patch.

Should You Wait for a Fix Instead of Troubleshooting?

No. Microsoft has not listed a known issue for KB5124008 getting stuck, so there's no patch coming to fix the stuck installer itself. The fixes above resolve the vast majority of cases within 15 to 30 minutes.

If you've tried every step here and the update still won't move past 0%, deeper corruption in the Windows Update components is the cause. At this stage, an in-place upgrade using the Windows 11 Installation Assistant repairs the update infrastructure without touching your files or installed programs, and installs KB5124008 as part of the process.

Key Takeaways

• KB5124008 stuck at 0% usually comes from a corrupted update cache, a stalled BITS service, or low disk space, not a broken update file.
• Restarting Windows Update, BITS, and Cryptographic Services, then clearing the SoftwareDistribution Download folder, fixes most stuck installs.
• If the service restart doesn't work, run DISM and SFC, or download the .msu file directly from the Microsoft Update Catalog.
• Keep at least 20 GB free on your system drive before installing any 24H2 or 25H2 cumulative update.