September 2026 Patch Tuesday Is Breaking Remote Desktop…

The short version

The September 2026 Patch Tuesday cumulative updates — KB5122876 for Server 2019, KB5122882 for Server 2022, and KB5122871 for Server 2025 — are causing Remote Desktop Services to hang and stop accepting connections. Servers typically work for a few hours after the update, then fail. Rolling back the update restores RDS, but removes the month’s security fixes. Microsoft is investigating and has not published an official workaround as of 11 September 2026.

⚠ Action required for RDS teams: If you have not yet deployed the September 2026 Patch Tuesday updates to Windows Server machines running Remote Desktop Services, hold that deployment now. Validate your environment carefully before proceeding. This is community-reported — no official Microsoft fix or workaround exists as of 11 September 2026.

What is happening

Windows Server administrators are reporting a serious regression after installing the September 2026 Patch Tuesday cumulative updates. Remote Desktop Services (RDS) — the component that enables users to connect to servers via Remote Desktop Protocol (RDP) and Terminal Services — is failing after the update is applied.

The failure is not immediate. Servers typically continue accepting Remote Desktop connections normally for a few hours after the update is installed. The problems begin once users start logging out. After the first batch of logouts, the Remote Desktop Services stack enters an unresponsive state. Existing sessions become unable to disconnect or log off cleanly. New connection attempts hang at the connection screen and eventually fail. In some cases, the only way to recover the server is a hard reset.

One administrator debugging the issue on Server 2022 identified what appears to be a deadlock inside the RDP service stack. The service hangs at RDPSERVERBASE!WDLIB_Close with no timeout configured, creating a deadlock between the Remote Desktop service and the Local Session Manager (LSM). Microsoft has not confirmed this as the definitive root cause, but the behaviour matches what multiple administrators are independently observing.

📋 Note: This is a community-reported issue. BleepingComputer reported it on 10 September 2026 based on administrator reports from Reddit threads and reader submissions. Microsoft told BleepingComputer it is aware and investigating. No official Knowledge Base article has been published for this specific regression as of 11 September 2026.

The issue affects all three current Windows Server releases and has been reproduced across multiple independent environments, covering Terminal Server deployments and general RDS configurations.

Who is affected

Any Windows Server running Remote Desktop Services that has received the September 2026 Patch Tuesday update is at risk. The issue is not tied to a specific hardware configuration, hypervisor, or third-party software — it follows the update across different environments.

Windows Server version	Update KB	Affected?
Windows Server 2019	KB5122876	✅ Yes — confirmed affected
Windows Server 2022	KB5122882	✅ Yes — confirmed affected
Windows Server 2025	KB5122871	✅ Yes — confirmed affected
Servers not yet patched with September 2026 updates	N/A	❌ Not yet affected — hold deployment
Client Windows 11 / Windows 10 devices	N/A	❌ Not reported as affected by this specific issue

Administrators running Terminal Server farms where users log in and out throughout the day are the most heavily impacted, as the failure mode is triggered by user logouts. Servers that see low session turnover may not exhibit the problem until enough logouts have occurred.

How to tell if your environment is affected

The most direct way to confirm exposure is to check which September 2026 updates are installed on your RDS servers. You can do this from an elevated PowerShell session on each server.

PowerShell — Run as Administrator on RDS server

# Check if the September 2026 update is installed on Server 2019 Get-HotFix -Id KB5122876 # For Server 2022 Get-HotFix -Id KB5122882 # For Server 2025 Get-HotFix -Id KB5122871 # Returns the hotfix entry if installed # Returns nothing (no output) if NOT installed

If the relevant KB is returned, the update is installed and RDS is at risk. To check the current state of the Remote Desktop Services stack, run the following:

PowerShell — Check RDS service state

# Check the three core RDS services Get-Service TermService, SessionEnv, UmRdpService | Select-Object Name, DisplayName, Status # Healthy output: # TermService Remote Desktop Services Running # SessionEnv Remote Desktop Configuration Running # UmRdpService Remote Desktop Services UserMode... Running # Affected output after the deadlock occurs: # TermService Remote Desktop Services Stopped (or Paused) # Note: a server restart may NOT restore the service # Rolling back the update is the confirmed recovery - restart alone does not always fix this

When the deadlock has occurred, the Event Viewer System log will contain errors from the TermService source. Look for these in the hours following user logouts:

⚠ Error — System Event Log — Source: TermService

Log: System
Source: TermService
Level: Error / Critical
Message: The Remote Desktop Services service terminated unexpectedly. This has occurred N time(s). The following corrective action will be taken in X milliseconds.
Related: Look for preceding SessionEnv errors indicating the Local Session Manager stopped responding during a logoff sequence

⚠ Gotcha: The failure is triggered by user logouts, not logins. A server that looks stable immediately after the update — because users have been logging in but not yet logging out — can enter the deadlock state hours later when the day’s first wave of logoffs begins. Do not assume a server is unaffected just because it worked normally for the first few hours post-update.

What you can do now

There is no official Microsoft-provided workaround as of 11 September 2026. The options available to administrators are to hold unpatched servers, roll back the update on patched servers, or keep servers patched while accepting the stability risk and monitoring closely.

Option 1 — Hold deployment (safest, for servers not yet patched):

If you have not yet deployed KB5122876, KB5122882, or KB5122871 to your RDS servers, pause that deployment in your patching tool (Windows Server Update Services, Microsoft Endpoint Configuration Manager, or Intune) until Microsoft confirms a resolution. This is the lowest-risk option and requires no change to already-deployed servers.

✅ Tip: Before resuming deployment, validate in a non-production RDS server by installing the update, running a full day of logon/logoff cycles, and confirming that Remote Desktop Services remain healthy after logouts. Only then promote to production.

Option 2 — Roll back the update (for servers already patched):

Administrators who have already deployed the September update and are experiencing failures can uninstall the cumulative update to restore Remote Desktop Services. On Windows Server, cumulative updates can be removed from an elevated Command Prompt or PowerShell session:

Command Prompt — Run as Administrator (select the correct KB for your OS)

# Windows Server 2019 — uninstall KB5122876 wusa.exe /uninstall /kb:5122876 /quiet /norestart # Windows Server 2022 — uninstall KB5122882 wusa.exe /uninstall /kb:5122882 /quiet /norestart # Windows Server 2025 — uninstall KB5122871 wusa.exe /uninstall /kb:5122871 /quiet /norestart # After the uninstall completes, restart the server # wusa /quiet suppresses the UI; /norestart lets you control the reboot window # Confirm removal with: Get-HotFix -Id KB5122876 (should return no output)

⚠ Warning: Rolling back the September 2026 cumulative update removes all security patches included in that release, including fixes for actively exploited vulnerabilities. This is a stability-vs-security trade-off. Assess your organisation’s risk posture before rolling back, and plan to reapply the patched update as soon as Microsoft provides a resolution. Consider additional network controls (firewall rules, VPN restrictions) to reduce exposure while RDS servers are in an unpatched state.

Option 3 — Open a Microsoft support case:

If your organisation is running RDS in a production environment with no ability to roll back, opening a support case with Microsoft is the appropriate path. Microsoft has acknowledged the reports and is investigating. A support case escalates the issue within Microsoft’s engineering teams and may surface a workaround (such as a specific registry key or service configuration) before a patched update is available.

Microsoft’s response

Microsoft confirmed to BleepingComputer on 10 September 2026 that it is aware of the reports and is actively investigating. No official Knowledge Base article, release-health entry, or workaround has been published for this issue as of 11 September 2026. The Windows Server release health dashboards on Microsoft Learn are the authoritative location for official updates:

Until a patched cumulative update or official workaround is available, the recommendation is to hold the September 2026 updates on any RDS server, roll back on servers already affected, and monitor the release health dashboards for updates.

References

Last reviewed: 11 September 2026. This post will be updated when Microsoft publishes an official fix or workaround.

September 2026 Patch Tuesday Is Breaking Remote Desktop Services on Windows Server