Windows admins report that the September 2026 cumulative updates are causing Remote Desktop Services (RDS) failures on Windows Server 2019, 2022, and 2025 systems, preventing users from connecting and, in some cases, requiring a hard reset to restore functionality.
The problems appear after installing this month’s Microsoft September 2026 Patch Tuesday cumulative updates, with many admins reporting on Reddit [1, 2, 3] that RDS servers work normally for a few hours before connections start failing.
Once a server starts failing, existing Remote Desktop sessions may not be able to disconnect or log off properly. New connection attempts can also hang during the connection process and eventually fail.
Source: Reddit
BleepingComputer has also received reports from readers who say their Terminal Servers began experiencing similar problems after installing the September updates.
“All terminal servers in our environment are failing (sessions dropping, no new connections possible, only solution is a hard reset) within a day,” one reader posted to our Patch Tuesday article.
Another reader said Remote Desktop Services initially worked normally after installing the September update but began failing after users logged out.
“We’ve had issues with Remote Desktop Services post September update. It works initially, but after the first log out, services crash and no further users can sign in,” a Windows admin posted.
For them, restarting the server did not resolve the problem. However, rolling back the September update resolved the issues they were having.
Another administrator investigating Server 2022 reported on Reddit that the RDP service becomes unresponsive when users begin logging out and said debugging showed what appeared to be a deadlock between Remote Desktop and the Local Session Manager.
“The service hangs at RDPSERVERBASE!WDLIB_Close, there seems to be no timeout set here. This results in a deadlock between RDP and LSM,” reads the post.
However, Microsoft has not confirmed this as the cause of the failures.
The reports are affecting all Windows Server releases, with administrators reporting similar problems on Server 2019 (KB5122876), Server 2022 (KB5122882), and Server 2025 (KB5122871) systems.
Admins who have rolled back the September updates say doing so restores Remote Desktop functionality. However, removing the updates also removes the security fixes included in this month’s Patch Tuesday release.
Microsoft told BleepingComputer that it is aware of the reports and is investigating, and will share guidance as it becomes available.
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