On 2023-12-19, Microsoft released an out-of-band update to resolve Message Queuing (MSMQ) errors that emerged from recent security updates. The update, identified as KB5074976, is available via the Microsoft Update Catalog.
Update Impact and Scope
The December 2025 security updates initially caused malfunctions in MSMQ and applications relying on it, particularly affecting Windows 10 22H2, Windows Server 2019, and Windows Server 2016. Systems with updates KB5071546, KB5071544, and KB5071543 experienced inactive queues, resource errors on IIS sites, and application message writing failures.
Error Causes and Resolution
The root problem originated from changes in the MSMQ security model that altered permissions on the crucial system folder C:\Windows\System32\msmq\storage. Consequently, MSMQ users now require write access, previously exclusive to administrators. Systems under heavy load and users without administrative rights were severely impacted. Administrators faced challenges as reverting to previous updates was not a viable long-term solution.
Takeaway for Business and Tech
MSMQ is vital for asynchronous communication in business applications and IIS-based web apps. The quick response from Microsoft with the KB5074976 patch underscores the necessity of balancing security and functionality. Enterprises should apply the update to ensure the reliability of their messaging queues while remaining prepared for further updates related to MSMQ's security enhancements.
