Microsoft has released an out-of-band security update to address a significant vulnerability in Message Queuing (MSMQ) functionality that impacts Windows 10 systems running IIS web servers and enterprise environments.
The flaw, discovered and documented in the December 9, 2025 update (KB5071546), affects Windows 10 version 22H2 and version 21H2.
The Vulnerability
The MSMQ bug causes severe operational disruptions, particularly in clustered MSMQ environments experiencing high loads.
Organizations affected by this vulnerability have reported multiple critical symptoms including inactive message queues, insufficient resource errors, and applications unable to write to message queues.
The vulnerability manifests through various error conditions that severely hamper IT operations.
Users report error messages claiming insufficient disk space or memory, even when system resources are available.
The Message Queue service fails to create new messages, causing application failures and service interruptions.
These issues escalate dramatically in enterprise and managed IT environments where MSMQ handles large message volumes across distributed systems.
Notably, Microsoft confirmed that Windows Home and Pro edition users running personal devices are unlikely to encounter this issue.
The vulnerability primarily threatens enterprise-class deployments where MSMQ serves as a critical infrastructure component for application messaging and queue management.
The out-of-band patch directly addresses MSMQ functionality failures experienced after December 9, 2025 updates.
System administrators must apply KB5015684 to upgrade to Windows 10 version 22H2, which incorporates the MSMQ fix alongside other quality improvements.
Users with previously installed updates will automatically receive only new updates contained within this package.
Microsoft continues monitoring for additional MSMQ-related issues and maintains updated guidance through the Windows release health dashboard.
For comprehensive security information, administrators should consult the Security Update Guide and December 2025 Security Updates documentation published on Microsoft’s official channels.
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