Microsoft has asked businesses to reach out for advice on how to temporarily mitigate a known Message Queuing (MSMQ) issue causing enterprise apps and Internet Information Services (IIS) sites to fail.

MSMQ is an optional Windows service commonly used in enterprise environments that helps apps communicate over a network.

The known issue mainly affects enterprise users with Windows 10 22H2, Windows Server 2019, and Windows Server 2016 devices that have installed the KB5071546, KB5071544, and KB5071543 security updates released during the December 2025 Patch Tuesday.

While Microsoft is investigating it and working on a fix, in a Tuesday update to the Windows release health dashboard, it advised enterprise customers to reach out for details on how to temporarily mitigate this bug in their environments.

"Individuals using Windows Home or Pro editions on personal devices are very unlikely to experience this issue. This issue primarily affects enterprise or managed IT environments," Microsoft said. "A workaround is available for affected devices. To apply the workaround and mitigate this issue in your organization, please contact Microsoft Support for business."

As Microsoft explained when it acknowledged the issue on Monday, affected users are experiencing a wide range of symptoms, from inactive MSMQ queues and applications unable to write to queues to IIS sites failing with "insufficient resources" errors. Some impacted systems are also displaying misleading "There is insufficient disk space or memory" messages, even though sufficient resources are available.

The problem stems from changes to the MSMQ security model that have modified permissions on a critical system folder, requiring MSMQ users to have write access to a directory that is usually restricted to administrators.

"This issue is caused by the recent changes introduced to the MSMQ security model and NTFS permissions on C:\Windows\System32\MSMQ\storage folder. MSMQ users now require write access to this folder, which is normally restricted to administrators," Microsoft explained. "As a result, attempts to send messages via MSMQ APIs might fail with resource errors. This issue also impacts clustered MSMQ environments under load."

Microsoft has yet to provide a timeline for when a fix will be available and has not confirmed whether it will issue an emergency update or wait for the next scheduled release. For now, IT admins dealing with this issue should reach out to Microsoft's business support team for a temporary workaround or may need to consider rolling back the updates.

In July, Microsoft also asked businesses to reach out for advice on how to work around another known issue causing Cluster service and VM restart problems after installing the July 2025 Windows Server 2019 security updates.