Microsoft Investigates RDS Failures After September Windows Server Updates

September 2026 Windows Server updates are causing Remote Desktop Services failures, with administrators reporting frozen RDS hosts, failed connections, and servers that sometimes require a hard reset.

Remote Desktop Services can stop working hours after the update

Windows administrators report Remote Desktop Services problems after installing the September 2026 cumulative updates.

The issue does not always appear immediately. Some RDS servers reportedly continue working normally for several hours before Remote Desktop connections start failing.

Existing sessions can become unable to disconnect or log off correctly, while new connection attempts may hang before eventually failing. Some administrators say the failures begin after users start logging out of active sessions.

In more severe cases, restarting the server does not restore RDS functionality, forcing administrators to perform a hard reset.

Windows Server 2019, 2022, and 2025 appear affected

Reports currently involve all three supported Windows Server releases and their September cumulative updates:

• Windows Server 2019: KB5122876
• Windows Server 2022: KB5122882
• Windows Server 2025: KB5122871

The similar behavior across these releases suggests the problem is not limited to a single Windows Server version.

A possible Remote Desktop deadlock is under investigation

One administrator debugging the problem on Windows Server 2022 found that the RDP service became unresponsive when users started logging out.

Their debugging pointed to a possible deadlock involving Remote Desktop and the Local Session Manager.

The service reportedly becomes stuck at RDPSERVERBASE!WDLIB_Close, where there may be no timeout mechanism to recover automatically.

Microsoft has not confirmed that this deadlock causes the wider RDS failures.

Rolling back the update can restore RDS

Administrators report that removing the September cumulative update restores Remote Desktop functionality.

However, rolling back the update creates a significant security tradeoff because September’s Patch Tuesday updates address 966 security flaws.

Microsoft says it is aware of the Remote Desktop Services reports and is investigating the issue. The company says it will provide additional guidance as more information becomes available.

Via BleepingComputer