Microsoft's September 2026 cumulative updates are reportedly causing widespread failures in Remote Desktop Services (RDS) across various Windows Server versions, preventing users from connecting to servers and, in some cases, necessitating hard reboots to restore functionality. The issues have been observed on Windows Server 2019, 2022, and 2025 systems following the installation of the monthly Patch Tuesday updates.
Administrators have reported that RDS servers initially function normally for a few hours after the updates are applied. However, connections subsequently begin to fail, with existing Remote Desktop sessions unable to disconnect or log off properly. New connection attempts often hang during the process before ultimately failing.
The problem appears to affect all current Windows Server releases. Specifically, administrators have linked the issues to update KB5122876 for Server 2019, KB5122882 for Server 2022, and KB5122871 for Server 2025.
Several reports indicate that once a server begins to experience these failures, a simple restart may not resolve the problem. Some administrators have found that the only effective solution is to perform a hard reset. Others have noted that rolling back the September updates completely restores Remote Desktop functionality.
One administrator investigating a Server 2022 system reported that the RDP service becomes unresponsive when users log out. Debugging suggested a potential deadlock between Remote Desktop and the Local Session Manager, with the service hanging at `RDPSERVERBASE!WDLIB_Close` due to what appeared to be an unset timeout. However, Microsoft has not confirmed this as the underlying cause.
While rolling back the updates resolves the RDS issues, it also removes the security fixes included in the September Patch Tuesday release, leaving systems potentially vulnerable. Microsoft has not yet issued a statement or provided a fix or mitigation for the reported problems.
