[German]The Microsoft security updates released on September 8, 2026, cause RDP connections to stop working after the patches are installed. Users are logged out and can no longer log in. Microsoft has now confirmed this; all versions of Windows are affected.
Note: Use the German blog's build in translation feature to read the German blog posts linked below in English.
Windows Updates (Sept. 2026) with RDP issues
For Windows Server 2016 through Windows Server 2025, Microsoft released security updates on September 8, 2026, for the versions still supported. I have listed the relevant updates, along with the fixes, in the blog post "Patchday: Windows Server-Updates (September 8, 2026)." For clients running Windows 10 and Windows 11, the updates are listed in the post "Patchday: Windows 10/11 Updates (September 8, 2026)." Microsoft's support articles indicate that a change has been made to Remote Desktop. The list of fixed bugs states:
[Remote Desktop] This update improves Remote Desktop audio redirection, helping audio from remote sessions play correctly on the local device.
The vulnerabilities fixed in the September 2026 security update are mentioned in the post " Microsoft Security Update Summary (September 8, 2026)."
Shortly after the security updates were released, administrators began posting on the blog, reporting issues with Remote Desktop connections. Users are being logged out and are unable to log back in. Some administrators also reported performance issues on Windows Server. I covered these issues in the blog post "Windows Server: RDP-Nutzer fliegen nach Sept. 2026-Update aus Session".
Microsoft Confirms RDS Issues
German blog reader Jörg Maletzky pointed out in this comment on the post "Remote Desktop Services might stop responding after Sept. 2026 security update" that Microsoft had listed the issues in the "Known Issues" section of the Windows Server 2025 Release Health Dashboard. There, Microsoft confirms the issues I listed in the blog post above and writes:
Some Windows devices with Remote Desktop enabled might experience Remote Desktop Services (RDS) instability.
It sounds kind of funny when people talk about "instabilities" in Remote Desktop Services (RDS) on some Windows devices. The linked support article cites Update KB5122871 from September 8, 2026, for Windows Server 2026 as the cause. But it apparently affects all updates from September 2026 in this area that made changes to the Remote Desktop Service.
Microsoft states that in some environments, RDS may become unstable. This can cause RDP connections to time out after a few minutes, lead to login issues, or cause servers to get stuck on the message "Please wait while the Remote Desktop configuration is completed."
Related tools such as the Microsoft Management Console (MMC), the RDS License Diagnostic Tool, and File Explorer may also stop responding. In addition, the Windows Update page may stop responding and continuously display a loading indicator. The following are all affected:
- Windows Clients: Windows 11 23H2, Windows 11 24H2 – 25H2, Windows 11 – 26H1 (ARM), Windows 10 21H2 – 22H2, Windows 10 Enterprise LTSC 2019; Windows 10 Enterprise LTSC 2016
- Windows Server: Windows Server 2025; Windows Server 2022; Windows Server 2019; Windows Server 2016; Windows Server 2012 R2; Windows Server 2012
If the September 2026 updates are installed (although I am not aware of any updates for Windows Server 2012 R2 and Windows Server 2012).
A Workaround from Microsoft
Microsoft suggests the following workaround for affected administrators: If access to a virtual machine via RDP is no longer possible, customers may be able to temporarily restore the connection by pausing (unlocking) and restarting the affected virtual machine.
However, that probably won't help with bare-metal installations. Readers on the German blog have suggested disabling Remote Audio. Microsoft made some changes in this area as part of the September 2026 patch day. That would also explain why not all users are affected. Those affected can leave a comment to let us know if disabling Remote Audio works. Microsoft is currently investigating the issue.
Similar articles:
Microsoft Security Update Summary (8. September 2026)
Patchday: Windows 10/11 Updates (8. September 2026)
Patchday: Windows Server-Updates (8. September 2026)
Patchday: Microsoft Office Updates (8. September 2026)
Exchange Server: Sicherheitsupdates (8. September 2026)
Microsoft Office: Update vom 8. September 2026 macht (Excel-)Probleme (Copy&Paste)
Windows Server: RDP-Nutzer fliegen nach Sept. 2026-Updat aus Session
Windows 11 24H2 – 25H2: Preview Update KB5120998 (27. August 2026)
Windows 11 24H2/25H2 Preview Update KB5120998: Microsoft bestätigt Mauszeiger-Probleme
Windows 11 24H2/25H2 Preview Update KB5120998: Microsoft bestätigt Desktop-Hintergrund-Problem
Windows 11: Outlook- und Teams-Startprobleme auf ARM behoben
September 2026-Updates fixen Mauszeiger- & Desktop-Wallpaper-Bugs und ARM App-Crashes
WSUS-Sync-Problem durch September 2026-Updates gefixt?
Windows September 2026 Patchday-Nachlese: Schwarzer Bildschirm, Secure Boot, Vertrauensstellung zur Domäne
