Microsoft December 2025 Security Updates Disrupt MSMQ Functionality on IIS

A significant compatibility issue has been introduced by Microsoft’s December 2025 security update, affecting Message Queuing (MSMQ) functionality across Windows Server and client environments.

The update in question, identified as KB5071546 (OS Build 19045.6691), was released on December 9, 2025, and has already had an impact on organizations that rely on MSMQ for inter-application communication, particularly in Internet Information Services (IIS) deployments.

Organizations experiencing the issue are reporting multiple critical failures that are affecting their messaging infrastructure.

MSMQ queues are becoming inactive, resulting in IIS sites failing with “Insufficient resources to perform operation” errors.

Applications attempting to write to message queues are encountering failures, while system logs are displaying misleading error messages that reference insufficient disk space or memory, despite there being adequate resources available.

One of the most concerning symptoms is the generation of errors, such as “The message file ‘C:\Windows\System32\msmq\storage*.mq’ cannot be created,” when attempting to create message files.

Clustered MSMQ environments that are operating under heavy load appear to be 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:\Windows\System32\MSMQ\storage 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 affects 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 highlights the importance of comprehensive testing before deploying security updates in production environments, particularly for systems that rely on specialized messaging infrastructure.