Microsoft: December Security Updates Cause Message Queuing Failures

Microsoft has confirmed that the December 2025 security updates are breaking Message Queuing (MSMQ) functionality, affecting enterprise applications and Internet Information Services (IIS) websites.

This known issue affects Windows 10 22H2, Windows Server 2019, and Windows Server 2016 systems that have installed the KB5071546, KB5071544, and KB5071543 security updates released during this month's Patch Tuesday.

On impacted systems, users are experiencing a wide range of symptoms, from inactive MSMQ queues and IIS sites failing with "insufficient resources" errors to applications unable to write to queues. Some systems are also displaying misleading "There is insufficient disk space or memory," despite having more than enough resources available.

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

This means that the known issue will not affect devices where the users are logged in with an account that grants them full administrative privileges.

"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."

The MSMQ service is available on all Windows operating systems as an optional component. It provides applications with network communication capabilities and is commonly used in enterprise environments.

Microsoft is investigating the issue but has not provided a timeline for a fix or confirmed whether it will wait for the next scheduled release or issue an emergency update. For now, admins facing this issue may need to consider rolling back the updates, though that raises its own security concerns.

In April 2023, Microsoft also warned IT admins to patch a critical vulnerability (CVE-2023-21554) in the MSMQ service that exposed hundreds of systems to remote code execution attacks.

Source: BleepingComputer