Advisories
September Windows Server Security Updates Trigger Critical Remote Desktop Deadlocks
Microsoft's September 2026 cumulative updates for Windows Server are causing severe stability issues across Remote Desktop Services. System administrators report that installations on Windows Server 2019, 2022, and 2025 lead to frozen RDP sessions, failed logins, and full system hangs requiring hard reboots. Preliminary technical analysis points to a service deadlock during user logouts. While Microsoft is actively investigating, removing the updates restores functionality at the cost of leaving systems exposed to unpatched security vulnerabilities.
Patch Tuesday Releases Cause Operational Havoc on RDS Deployments
System administrators deploying Microsoft's September 2026 security updates are encountering major disruptions across Windows Server environments. Reports indicate that cumulative updates KB5122876, KB5122882, and KB5122871—targeting Windows Server 2019, 2022, and 2025 respectively—cause Remote Desktop Services (RDS) to freeze, preventing remote users from establishing or ending sessions.
The failures typically manifest several hours after deployment or immediately following the first batch of user logouts. Once triggered, existing remote desktop connections drop, new connection attempts hang indefinitely, and standard service restarts fail to resolve the unresponsiveness. In many cases, infrastructure engineers are forced to perform hard system resets to regain control over affected hosts.
Deadlock Between RDP and Local Session Manager
Independent analysis from IT administrators points to a potential deadlock involving the Remote Desktop infrastructure and the Local Session Manager. Debugging traces highlight that the service stalls at RDPSERVERBASE!WDLIB_Close due to an apparent lack of timeout controls when handling session terminations.
Key symptoms impacting updated servers include:
- Inability to process new incoming RDP connection requests.
- Frozen user sessions during disconnection or sign-out operations.
- Unresponsive Remote Desktop management services requiring physical or hard virtual reboots.
Remediation Trade-Offs and Microsoft Response
Microsoft has acknowledged the ongoing issues and confirmed an active investigation into the underlying bug. Currently, the only verified mitigation is rolling back the September cumulative updates, which successfully restores remote access functionality. However, security teams face a critical dilemma: uninstalling the patches strips away the essential security fixes delivered in this month's security release, leaving infrastructure exposed to potential threats until an official fix is made available.
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