Windows 11 September 2026 Update: Problems, Fixes & What You Need to Know
Microsoft released its September 2026 security updates for Windows 11, including KB5124008 for Windows 11 versions 24H2 and 25H2.
While the update includes security improvements and system fixes, Microsoft has also documented several issues affecting some users. These include problems with Remote Desktop Services, USB Audio devices, Hyper-V Linux virtual machines, and File History.
Some of the reported issues have already been resolved through later updates, while the File History problem is still being investigated.
Here is what Windows 11 users should know about the September 2026 update.
What Is the Windows 11 September 2026 Update?
The September 8, 2026 security update KB5124008 applies to Windows 11 versions 24H2 and 25H2.
Microsoft says the update includes security improvements and servicing changes designed to improve the reliability of Windows Update installation.
Microsoft also continues updating Secure Boot certificates through Windows Update as older certificates begin reaching expiration.
1. Remote Desktop Problems
One of the issues reported after the September security update involved Remote Desktop Services (RDS).
Some affected environments experienced:
- RDP connections failing after several minutes
- Sign-in problems
- Remote Desktop Configuration getting stuck
- Microsoft Management Console becoming unresponsive
- File Explorer becoming unresponsive
- Windows Update pages continuously loading
Microsoft later resolved the issue through updates released from September 14 onward, including KB5129195 for affected Windows 11 versions.
What should you do?
If you experienced Remote Desktop problems after the September update, check:
Settings → Windows Update → Check for updates
Install the latest available update rather than relying only on the original September 8 update.
2. USB Audio Problems
Microsoft also documented problems affecting some USB Audio Class 1.0 devices.
Possible symptoms include:
- No sound output
- Code 10 in Device Manager
- Volume controls not responding
- Sound settings becoming unavailable
- Problems with multichannel audio
Microsoft released an out-of-band update on September 14 that resolved the issue affecting some 8-channel and 3D audio configurations. Other symptoms were still being addressed according to Microsoft's latest documentation.
If your USB audio device is affected, make sure Windows is fully updated before attempting more advanced troubleshooting.
3. Hyper-V and Linux VM Folder Sharing
Another documented issue affected some Hyper-V-based Linux virtual machines.
The problem involved Plan9 host folder shares, which could become unavailable after installing the September security update.
Microsoft lists this issue as resolved through later updates, including KB5129195 for affected versions.
This issue is mainly relevant to users running virtualization environments and Linux VMs rather than typical Windows desktop users.
4. File History May Stop Working
The most important currently documented issue for some users involves File History.
File History is a Windows feature that can back up files to an external drive or network location.
After installing KB5124008, some users may experience:
- File History failing to create backups
- Existing backups not being updated
- A message saying "Reconnect your drive"
- The Last Backup date not updating
- Previously backed-up files showing "No previous version available"
- FileHistory.exe-related crashes appearing in Event Viewer
Microsoft says it is working on a resolution in a future Windows update.
Important
If you rely on File History for important files, don't assume that a successful connection means that new backups are actually being created.
Check the backup status manually and keep another backup method for important data.
How to Check Your Windows 11 Version
To check your Windows version:
- Press Windows + R
- Type:
winver
- Press Enter
You can then see your Windows version and OS build.
You can also go to:
Settings → System → About
How to Check for the Latest Windows Update
The easiest method is:
Settings → Windows Update → Check for updates
If Microsoft has released a newer cumulative or out-of-band update for your device, Windows Update should offer it according to your device's configuration.
Microsoft recommends installing the latest available update because it can contain fixes for previously documented issues.
Should You Uninstall the September Update?
If your computer is working normally, there is generally no reason to remove a security update simply because some issues have been reported.
Instead:
- Check your Windows version.
- Check Windows Update.
- Install the latest available updates.
- Restart the PC if required.
- Check whether the specific problem remains.
If you have a serious problem after an update, check Microsoft's official Windows release-health documentation before making advanced system changes.
Official Microsoft Links
Windows 11 KB5124008
Windows 11 Known Issues
Microsoft Learn — Windows 11 Release Health
Windows 11 26H1 Release Health
Microsoft Learn — Windows 11 26H1
Windows Update
Microsoft Support — Windows Update
Final Thoughts
The September 2026 Windows 11 updates bring important security and system improvements, but Microsoft has also documented several compatibility and reliability issues.
The good news is that Remote Desktop and Hyper-V folder-sharing issues have received fixes through subsequent updates, while the File History problem remains under investigation according to Microsoft's latest documentation.
If your PC is working normally, the practical step is to keep Windows updated and regularly check Microsoft's Windows Release Health pages for newly documented issues.
Disclaimer: This article is for informational purposes. Windows issues and their resolutions can change as Microsoft releases additional updates.