Microsoft’s December 2025 security update has introduced a significant compatibility issue affecting Message Queuing (MSMQ) functionality across Windows Server and client environments.
The problematic update, identified as KB5071546 (OS Build 19045.6691), was released on December 9, 2025, and has already impacted organizations relying on MSMQ for inter-application communication, particularly in Internet Information Services (IIS) deployments.
Organizations experiencing the issue are reporting multiple critical failures affecting their messaging infrastructure.
MSMQ queues are becoming inactive, causing IIS sites to fail with “Insufficient resources to perform operation” errors.
Applications attempting to write to message queues encounter failures, while system logs display misleading error messages referencing insufficient disk space or memory despite adequate resources being available.
The most concerning symptom involves the generation of errors such as “The message file ‘C:WindowsSystem32msmqstorage*.mq’ cannot be created” when attempting to create message files.
Clustered MSMQ environments operating under heavy load appear particularly vulnerable to these disruptions, potentially affecting critical business operations across multiple servers simultaneously.
Root Cause Analysis
Microsoft has identified the root cause as recent changes to the MSMQ security model and NTFS permissions applied to the C:WindowsSystem32MSMQstorage folder.
The update implemented stricter permission controls, now requiring write access to this directory for standard MSMQ operations.
However, this folder remains restricted to administrators by default, creating a fundamental access conflict that prevents applications from writing messages to queues.
This permission mismatch represents a significant oversight in the security update’s deployment, as it breaks existing functionality without providing clear mitigation paths for affected users.
The issue impacts Windows 10 version 22H2 and Windows Server environments including Windows Server 2019 and Windows Server 2016.
Microsoft confirmed the issue on December 12, 2025, at 17:13 PT, indicating awareness of the problem shortly after user reports surfaced.
Microsoft is actively investigating the issue and has committed to providing updated information as the investigation progresses.
Organizations experiencing MSMQ failures should evaluate temporary workarounds while awaiting an official patch.
Administrators should monitor Microsoft’s security update portal for resolution details and patch availability.
The incident underscores the importance of comprehensive testing before deploying security updates in production environments, particularly for systems relying on specialized messaging infrastructure.
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