Microsoft: Windows 10 December Patch Breaks MSMQ, Causing App and IIS Sites Failures

Last Tuesday, Microsoft rolled out its mandatory December Patch Tuesday updates for Windows 10 users who are enrolled in the ESU program. While the updates were meant to improve security and stability, Microsoft has confirmed that the update, KB5071546, has introduced a serious issue affecting Message Queuing (MSMQ) (via Windows Latest).

For the uninitiated, MSMQ is a Windows feature used by applications and services to send messages reliably. The good part about this feature is that it even works when systems are under heavy load or temporarily offline. Notably, it’s commonly used in enterprise environments, IIS-based apps, and clustered setups where background communication is critical.

Following the latest update, users running MSMQ may start seeing failures, especially in high-load or clustered environments. Microsoft, in its documentation, notes:

Due to this issue, users might encounter the following symptoms:

• MSMQ queues becoming inactive
• IIS sites failing with “Insufficient resources to perform operation” errors
• Applications unable to write to queues
• Errors such as “The message file ‘C:\Windows\System32\msmq\storage*.mq’ cannot be created” when creating message files
• Misleading logs, such as “There is insufficient disk space or memory”, despite sufficient disk space and memory being available

Microsoft confirmed that the issue triggered after it made some changes to the MSMQ security model and NTFS permissions on the C:\Windows\System32\MSMQ\storage folder. MSMQ users now require write access to this folder, which is normally restricted to administrators. As a result, when you try to send messages via MSMQ APIs, it might fail with resource errors.

As of now, there’s no fix for the issue. However, Microsoft says that it’s investigating the issue and has assured users share more details once available. If you’re an admin, we recommend that you continuously monitor MSMQ-dependent services until an official fix or workaround is announced.