Microsoft Released Out-of-band Update to Fix MSMQ Bug that Impacts IIS Sites

Microsoft has deployed an emergency out-of-band update to address a significant issue with Message Queuing (MSMQ) functionality that emerged following the December 9 security patches.

The update, released on December 18, 2025, targets Windows 10 versions 22H2 and 21H2 through OS Builds 19044.6693 and 19045.6693.

The MSMQ vulnerability became apparent after users installed the previous month’s Windows updates. This causes message queues to become inactive and prevents applications from writing to queues.

Affected users encountered error messages due to insufficient resources, disk space, or memory constraints.

The issue is particularly problematic in clustered MSMQ environments under heavy load, where queue failures can cascade across distributed systems.

MSMQ Bug Fixed

Internet Information Services (IIS) sites that rely on MSMQ for asynchronous message processing are at risk of service disruptions without this patch.

Enterprise environments and managed IT infrastructures are most affected, though personal Windows Home and Pro editions remain largely unaffected.

The December 18 update incorporates all fixes from the previous December 9 release, meaning users who have not yet installed that month’s patches will receive both cumulative improvements.

Additionally, a servicing stack update (KB5068780) enhances verification logic for Azure-hosted devices, ensuring seamless future update installation on cloud infrastructure.

Microsoft emphasizes the importance of installing the latest servicing stack update before applying additional patches to prevent deployment complications.

Azure customers should verify that devices have access to the certificate update domains for successful installation. Administrators should prioritize deploying this out-of-band update across enterprise environments immediately.

Organizations running IIS with MSMQ integration should test the patch in staging environments before deploying it to production. The update is available through Windows Update, Business Update Catalog, and Server Update Services channels.

Separately, Microsoft warns that Secure Boot certificates will expire starting in June 2026, potentially affecting device boot capabilities.

Organizations should review certificate guidance and schedule updates proactively to prevent future operational disruptions.

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