Microsoft released an out-of-band update (KB5074976) on December 19 to address Message Queuing (MSMQ) errors caused by December 2025 security updates. These updates have led to operational disruptions in business applications and IIS websites, particularly on systems running Windows 10 22H2, Windows Server 2019, and Windows Server 2016, which received updates KB5071546, KB5071544, and KB5071543. Users reported issues such as inactive MSMQ queues, IIS sites generating "insufficient resources" error messages, and applications unable to write messages to queues. The problems stem from modifications in the MSMQ security model, which altered permissions for the system folder C:WindowsSystem32msmqstorage, requiring MSMQ users to have write access typically reserved for administrators. Systems with full administrative rights do not experience these issues. Microsoft is investigating the matter but has not provided a timeline for a resolution.