System administrators reported that Microsoft’s September 2026 cumulative security updates are causing outages in Remote Desktop Services (RDS) on Windows Server 2019, Windows Server 2022, and Windows Server 2025 servers. The outages prevent users from establishing new connections, while terminating or logging out of existing sessions may also become impossible. In some environments, this may require forcibly restarting the server.
The problems appeared after this month’s Patch Tuesday updates were installed. According to reports published by system administrators on Reddit and received by BleepingComputer from its readers, RDS servers may operate normally for several hours after the update before connections begin to fail. In other cases, the issue begins after users log out of their sessions, after which the service stops accepting new users.
Reported Symptoms
Symptoms include Remote Desktop connection attempts hanging, new sessions failing, and existing sessions being unable to disconnect or log out properly. One system administrator said that all Terminal Services servers in their environment began dropping sessions and blocking new connections within a day of installing the update, leaving a forced server restart as the only available solution.
Another administrator said that restarting the server did not resolve the issue, while removing the September update restored Remote Desktop Services functionality. An administrator investigating an outage on Server 2022 also said that the RDP service became unresponsive when users began logging out.
What Do We Know About the Cause?
One technical report published on Reddit pointed to a conflict or mutual wait condition between the Remote Desktop service and the Local Session Manager. The report’s author said the hang occurred at the RDPSERVERBASE!WDLIB_Close function, with no clear timeout, but Microsoft has not confirmed that this is the cause of the outages.
The reports are associated with the following updates: KB5122876 for Windows Server 2019, KB5122882 for Windows Server 2022, and KB5122871 for Windows Server 2025. The source does not establish that every server on which these packages are installed will be affected, but it explains that the reports span all three versions.
What Changes Practically for Server Administrators?
Removing the update restored the service in some environments, but it also removes the security fixes included in the Patch Tuesday release. Therefore, the source does not present rolling back the update as a safe or permanent solution, but rather as a measure some administrators used to restore access. The currently confirmed practical takeaway is the need to balance continued remote access with the risks of losing security patches until official guidance is issued.
certi.news reading: The importance of the reports lies not in a limited interface fault, but in their potential effect on the administrative and operational access infrastructure on which organizations rely for remote access. However, the technical cause remains unconfirmed, and at the time of publication Microsoft had neither authenticated the issue nor provided an official mitigation. The reports should therefore be treated as field indicators requiring verification in each environment, not as evidence that all Windows Server systems are affected.