- Microsoft's September 2026 Patch Tuesday cumulative updates have caused significant issues, including freezing sessions on Windows Server 2019, 2022, and 2025, which leads to RDP connections hanging indefinitely.
- Session hosts running Windows Server 2019, 2022, and 2025 have begun freezing hours after boot, leaving RDP connections stuck at 'Connecting...' and preventing users from logging off cleanly.
- Windows 11 updates have broken WSL and Claude Cowork due to issues with Plan9 folder shares, which are critical for these applications.
- Microsoft has acknowledged the Plan9 issue in its documentation and stated that it is working on a fix, although no official patch is available yet.
- Administrators have reported various workarounds, such as DISM removal or registry tweaks, but there is currently no official patch to resolve the issues caused by the September updates.
- The freezing issue on Windows Server occurs after a few hours of normal operation, typically triggered when a user session disconnects or reconnects.
- Event ID 20498 is generated in the TerminalServices-RemoteConnectionManager log when new RDP connection attempts hang, indicating that 'Remote Desktop Services has taken too long to complete the client connection.'
- The Plan9 issue in Windows 11 prevents shared folders from appearing, affecting applications like WSL and Claude Cowork, which rely on these shares.
Microsoft's September 2026 updates have led to widespread issues with Remote Desktop Services (RDS) on Windows Server 2019, 2022, and 2025, causing sessions to freeze and preventing users from logging off.26
The problems began immediately after the updates were released, with reports indicating that affected servers typically function normally for a few hours post-reboot before symptoms emerge.
The issue is triggered when a user session disconnects or reconnects, leading to new RDP connection attempts hanging indefinitely at the login screen. This generates Event ID 20498 in the logs, indicating that “Remote Desktop Services has taken too long to complete the client connection.”7
Affected administrators have noted that existing sessions cannot log off, and applications become unresponsive, with Task Manager freezing due to communication issues with the Local Session Manager.
Independent debugging suggests a deadlock in the RDP server base library during session teardown, although Microsoft has yet to confirm this root cause.
In addition to RDS issues, the updates have also disrupted applications like Claude Cowork and the Windows Subsystem for Linux (WSL), which rely on shared folders that are now inaccessible.
Currently, there are no official patches or fixes available, leaving users to navigate these challenges without guidance from Microsoft.
The same updates also addressed a critical Remote Desktop Services remote code execution flaw with a CVSS score of 9.8, highlighting the complexity of the situation.
“The RDS bug triggers Event ID 20498 and Winlogon 6005, with a deadlock in RDPSERVERBASE!WDLIB_Close. Administrators report that only a hard reset restores functionality, and the freeze often recurs later the same day.”
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