Remote Desktop Services Failures on Windows Servers Following September Update

Key Points:

• A critical bug affecting Remote Desktop Services (RDS) appeared immediately after Microsoft’s September 2026 Patch Tuesday updates, causing session hosts on Windows Server 2019, 2022, and 2025 to freeze hours after boot and leaving RDP connections stuck at “Connecting…”.
• The issue is linked to three specific cumulative updates (KB5122876, KB5122882, KB5122871) and manifests as deadlocks during session teardown, preventing users from disconnecting or logging off and causing system components like Task Manager and Settings to become unresponsive.
• Independent debugging points to a deadlock in the RDP server base library routine RDPSERVERBASE!WDLIB_Close, with affected hosts requiring hard resets to restore functionality; Microsoft has yet to confirm the root cause or respond publicly.
• The September updates also include critical security patches addressing nearly 1,000 vulnerabilities, including actively exploited zero-days and a high-severity RDS remote code execution flaw, complicating rollback decisions for administrators.
• Workarounds reported by administrators include uninstalling the update via DISM, disabling the problematic audio-redirection feature via registry keys, or forcing RDP to use TCP only; organizations are advised to test updates on non-critical hosts, monitor relevant event logs, and prepare rollback plans until an official fix is released.