Microsoft has issued an emergency out-of-band fix for a critical Hyper-V freeze bug impacting Windows Server 2022 environments configured with multiple NUMA nodes. The bug caused servers to fail to boot, disrupting enterprise virtualization infrastructures.

NUMA (Non-Uniform Memory Access) is a memory architecture used in high-performance multiprocessing systems, where memory is divided into nodes associated with specific CPUs. A bug introduced after the January security update KB5049983 caused memory mapping conflicts in systems with multiple NUMA nodes, leading to server freezes during startup.

This issue significantly affected virtualized data centers and enterprise environments utilizing Hyper-V for running virtual machines, causing operational bottlenecks. To address this, Microsoft released the patch KB5052819, an out-of-band update that fixes the memory allocation errors for systems with two or more NUMA nodes, enabling affected servers to boot normally.

Additionally, Microsoft released a servicing stack update KB5050117 to improve update reliability and reduce the risk of corrupted or incomplete installations.

Administrators are advised to:
- Check for updates via Windows Update on Windows Server 2022.
- Install the servicing stack update KB5050117 first.
- Apply the Hyper-V NUMA fix KB5052819.
- Restart servers during scheduled maintenance.
- Perform stress testing and monitor system stability post-update.

This incident highlights the importance of NUMA optimization in modern server infrastructures and reflects Microsoft's swift response to critical vulnerabilities. The improvements in update reliability aim to support large-scale and enterprise Windows Server deployments.

For further details and download instructions, administrators can consult Microsoft’s official documentation and update catalog entries for KB5052819 and KB5050117.