Quick answer: The September 8, 2026 Windows security update (KB5124008 on Windows 11 24H2 and 25H2) could make Remote Desktop Services unstable: RDP sessions dropped after a few minutes, sign-ins failed, or servers hung at “Please wait for the Remote Desktop Configuration”. Microsoft fixed it with out-of-band update KB5129195 on September 14, 2026, and every later monthly update includes the fix. Open Settings > Windows Update, select Check for updates and install what’s offered. Servers get their own fix KBs, listed below.
In this guide
What went wrong in September 2026
Microsoft logged the problem on its Windows release health page as “Remote Desktop Services might stop responding after Sept. 2026 security update”. It was opened on September 11 and marked resolved on September 14, 2026. Microsoft described these symptoms in organisations using RDS:
- RDP connections failing after several minutes
- Problems signing in to remote sessions
- Servers hanging at “Please wait for the Remote Desktop Configuration”
- MMC consoles, the RDS Licensing Diagnoser and File Explorer becoming unresponsive
- The Windows Update page in Settings spinning with a loading indicator
It affected a wide range of versions: Windows 11 26H1, 25H2, 24H2 and 23H2, Windows 10 22H2, 21H2 and the LTSC 2019 and LTSB 2016 editions, and Windows Server 2012 through 2025. Microsoft noted it didn’t affect Windows 365 or Azure Virtual Desktop.
It mainly hit machines acting as Remote Desktop hosts, such as RDS session hosts and servers. Microsoft didn’t say anything specific about Home edition, which can’t host Remote Desktop sessions anyway.
The fix: KB5129195 and its server versions
Microsoft’s release health entry says the issue “is resolved by the out-of-band (OOB) update released on September 14, 2026 (KB5129195), and in updates released after this date.” The update is cumulative, so it includes the September security fixes as well.
KB5129195 applies to Windows 11 24H2 and 25H2 and raises them to builds 26100.9457 and 26200.9457. Other versions got their own out-of-band updates the same week. The Server 2025 and 2022 entries below are from Microsoft’s pages; the rest come from admin reports that match Microsoft’s listings:
| Version | Fix update | Build after |
|---|---|---|
| Windows 11 24H2 / 25H2 | KB5129195 | 26100.9457 / 26200.9457 |
| Windows 11 23H2 | KB5129242 | 22631.7584 |
| Windows 11 26H1 | KB5129194 | 28000.2956 |
| Windows 10 22H2 / LTSC 2021 | KB5129236 | 19045.7727 / 19044.7727 |
| Windows Server 2025 | KB5129235 | 26100.33451 |
| Windows Server 2022 | KB5129237 | 20348.5631 |
| Windows Server 2019 / Windows 10 LTSC 2019 | KB5129238 | 17763.9247 |
| Windows Server 2016 / Windows 10 LTSB 2016 | KB5129239 | 14393.9514 |
| Windows Server 2012 R2 / 2012 | KB5129243 / KB5129244 | Monthly rollup |
Because later monthly updates include the fix, a PC or server that has installed the October 2026 update or newer is already covered. You only need the out-of-band package if a machine has been sitting on the September update.
How to install the fix
Windows 11 PCs
- Open Settings > Windows Update.
- Select Check for updates and install everything offered. Restart when asked.
If Windows Update is stuck loading, which was one of the symptoms, restart the PC and try again, or use these ways to force Windows Update.
Servers and manual installs
Microsoft says some of the server updates, including KB5129237 for Server 2022, are only available from the Microsoft Update Catalog. Search for the KB number, pick the package for your system (x64 or ARM64), download the .msu file and run it. Admins report that on Windows 11 24H2 and 25H2 a manual install needs the KB5043080 checkpoint update first if it isn’t already installed.
If you used Microsoft’s temporary Group Policy mitigation (a Known Issue Rollback) while waiting, Microsoft says you don’t need to undo it before installing the fix.
Check that you’re fixed
- Press Windows + R, type
winverand press Enter. - Compare the build with the table above. Any later build is fine too.
- Test an RDP connection, stay connected for a while, then disconnect and reconnect.
On servers, Settings > Windows Update > Update history (or Get-HotFix in PowerShell) shows which updates are installed.
If RDP still fails after updating
If the build is current and Remote Desktop still misbehaves, the September bug probably isn’t the cause. Restarting the service is a reasonable first check, although Microsoft doesn’t list it as a fix for this issue. Run Command Prompt as administrator on the host:
sc stop TermService
sc start TermService
sc query TermServiceOr in PowerShell as administrator:
Restart-Service -Name TermService -ForceThe service’s display name in services.msc is Remote Desktop Services. Restarting it disconnects everyone using the host, so warn users first.
For specific error messages, see “The function requested is not supported” and Remote Desktop error 0xC000000D. Some admins rolled back the September update as a stopgap; avoid that now, because it removes security fixes and the proper fix is available.
Known side effects to watch for
- Microsoft later listed KB5129195 among the updates that could make domain-joined PCs with Credential Guard lose their trust relationship with the domain on Windows 11 24H2, 25H2, 26H1 and 26H2. That issue was resolved by the September 22, 2026 update (KB5124010), so install the latest monthly update rather than stopping at KB5129195.
- KB5129195 also fixed host folder shares in Hyper-V Linux VMs, such as those used by WSL.
- Tech sites reported some USB audio problems continued after this update; see USB audio device shows Code 10 if that applies to you.
Related guides
- Remote Desktop error 0xC000000D: the token passed to the function is invalid (fix)
- Remote Desktop “The function requested is not supported”: how to fix it
- How to force Windows Update to check and install updates
- USB audio device shows Code 10 in Windows 11: how to fix it
Leave a Reply