When virtual machines malfunction unexpectedly, it can create significant challenges for administrators. Recently, such issues were reported with Windows Server 2022’s Hyper-V, prompting Microsoft to issue an emergency update.
Emergency Patch for Windows Server
After the latest patch deployment, users experienced multiple outages with Azure virtual machines, which would either hang or restart without warning. Microsoft has now addressed these concerns with an emergency fix.
Detailed Explanation of the Issue
The root of the problem was identified in the direct broadcast path for the physical guest address (GPA). This bug caused certain confidential virtual machines managed by Hyper-V to become unresponsive or restart spontaneously. Microsoft has acknowledged that this situation "impairs availability and requires manual intervention," indicating the severity of the problem that could disrupt entire networks.
Update KB5061906: The Resolution
To rectify this situation, Microsoft released the cumulative Out-of-band update KB5061906, which acts as a replacement for all prior updates for Windows Server 2022. However, it’s important to note that this update does not install automatically and is unavailable via Windows Update. Administrators will need to manually download the independent MSU package from the Microsoft Update Catalog.
Recommendations for Administrators
Microsoft highly recommends that IT professionals with Windows Server 2022 environments and Hyper-V installations install this update manually, especially if the May 2025 security update (KB5058385) has not yet been applied.
Release Notes
The update includes several quality improvements. Key highlights are as follows:
- Hyper-V Platform Issues: The update specifically addresses a problem in the GPA direct broadcast path that affects confidential Azure VMs, ensuring they function correctly without random restarts or failures.
- Maintenance Stack Update (KB5058531): This part of the patch enhances the servicing stack that installs Windows updates, ensuring more reliable and resilient operations moving forward.
For those operating with Windows Server 2022 utilizing Hyper-V, checking the environment and applying the KB5061906 update is crucial to maintaining system stability and preventing potential downtime.