Patchday Problem: Message Queuing issues in Windows 10, Server 2016, and 2019

Microsoft's December security update (KB5071546) is disrupting Message Queuing (MSMQ) on Windows 10 (including 22H2), Windows Server 2016 and 2019 — including clustered MSMQ under load — according to Windows Release Health Notes. Reported symptoms include MSMQ queues becoming inactive, IIS failures with “Insufficient resources to perform operation,” inability to write or create message files and misleading “insufficient disk space or memory” log entries. Microsoft attributes the breakage to changes in the MSMQ security model and NTFS permissions for C:\Windows\System32\MSMQ\storage that now require write access typically restricted to administrators and is investigating; the issue creates short-term operational risk for enterprise applications that depend on MSMQ until a patch or mitigation is issued.

Analysis

Microsoft's December 2025 security update KB5071546 has disrupted Message Queuing (MSMQ) on Windows 10 (including 22H2), Windows Server 2016 and 2019, with Microsoft acknowledging issues in its Windows Release Health Notes. Reported symptoms include MSMQ queues becoming inactive, IIS pages failing with "Insufficient resources to perform operation," failures to create message files such as "C:\Windows\System32\MSMQ\storage*.mq," and misleading "insufficient disk space or memory" log entries; clustered MSMQ environments under load are also affected.

Microsoft attributes the breakage to recent changes in the MSMQ security model and NTFS access controls that now require write access to C:\Windows\System32\MSMQ\storage, a directory typically restricted to administrators; as a result, MSMQ API calls can fail with resource errors. Microsoft is investigating and has not yet published a mitigation or hotfix timeline.

The incident creates immediate operational risk for enterprises and service providers that depend on MSMQ, raising the likelihood of application-level outages and potential SLA breaches until a corrective release or configuration guidance is issued. Market impact appears limited and sector-specific (sentiment moderately negative, market impact low), but investors should treat this as a material short-term availability risk for affected IT stacks and managed services providers.

Key Decisions for Investors

• Immediately require portfolio companies and IT-sensitive holdings to inventory dependence on MSMQ and Windows 10 22H2/Server 2016/2019 to quantify service and revenue exposure
• Advise operational teams to pause deployment of KB5071546 where feasible and, pending Microsoft guidance, evaluate temporary mitigations such as controlled permission adjustments or rollback procedures under change-control to restore MSMQ writes
• Monitor Microsoft's Release Health Notes and KB updates closely for a remediation timeline and vendor advisories, and adjust near-term operational risk assumptions and stress-tests accordingly
• Consider short-duration hedges or reduced exposure to externally facing software and managed-service providers with material MSMQ reliance if mitigation timelines remain unclear or SLA breach risk is high