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Is my IIS application crashing because of the Windows 10 December 2025 MSMQ update bug?
Windows 10 ESU Update KB5071546 Disrupts MSMQ Functionality
Microsoft recently confirmed a significant technical issue impacting enterprise environments following the December 2025 Patch Tuesday. The specific update, KB5071546, targets Windows 10 devices enrolled in the Extended Security Update (ESU) program. This patch introduces a critical bug affecting Microsoft Message Queuing (MSMQ), causing background services to fail and blocking applications dependent on asynchronous messaging.
This incident primarily impacts business infrastructure. Consumer devices rarely utilize MSMQ components and remain largely unaffected. However, system administrators managing IIS (Internet Information Services) or enterprise-grade applications on Windows 10 or Windows Server 2019 (via update KB5071544) must address this immediately to restore service stability.
Technical Root Cause: Permission Modification
The failure stems from an undocumented change in how the update handles NTFS security descriptors. The patch modifies the access control lists (ACLs) for the MSMQ storage directory.
Affected Path:
C:\Windows\System32\MSMQ\storage
Before the update, service accounts such as IIS AppPool Identity, NetworkService, or LocalService possessed the necessary read/write permissions for this folder. Post-update analysis reveals that the NTFS Security Descriptor shifts from D:P (Protected) to D:PAI (Protected, Auto-Inherited). This alteration inadvertently revokes write access for these essential service accounts.
Consequently, when the MSMQ service attempts to queue data, it encounters a “Access Denied” state at the file system level. The service cannot generate message files, causing the queue to enter an inactive state or refuse connections entirely.
Identifying the Symptoms
Administrators will observe immediate instability in dependent applications. If your infrastructure relies on MSMQ for background task management or IIS hosting, look for the following specific error signature in your event logs or application monitors:
System.Messaging.MessageQueueException: Insufficient resources to perform operation.
Additionally, IIS applications may cease functioning, returning HTTP 500 errors, while the MSMQ service itself may report “insufficient disk space or memory,” despite ample hardware resources being available.
Remediation Strategy
Microsoft is currently investigating the flaw, but no official hotfix exists as of December 16, 2025. The only confirmed resolution involves removing the problematic update to restore previous permission structures.
Steps to Rollback:
- Navigate to Settings > Update & Security > Windows Update.
- Select View update history.
- Click Uninstall updates.
- Locate KB5071546 (for Windows 10) or KB5071544 (for Windows Server 2019).
- Right-click the entry and select Uninstall.
- Reboot the server or workstation to apply changes.
Once the system restarts, the MSMQ service should automatically regain write access to the storage directory, and dependent queues will resume normal operation. Pause updates temporarily to prevent re-installation until Microsoft releases a revised patch.