Microsoft confirmed that the December 2025 security update (KB5071546) introduced a known issue breaking Message Queuing (MSMQ) functionality, primarily impacting enterprise applications relying on background tasks and IIS sites, causing 'Insufficient resources' errors. Admins must uninstall the update (KB5071546) for Windows 10 ESU PCs and Windows Server 2019 to restore service, as Microsoft investigates a fix. MSFT stock is currently trading slightly down pre-market at $473.78 (-0.22%).