Microsoft has issued an emergency fix for a critical issue affecting Windows Server 2025, specifically targeting the Hyper-V platform. This update is designed to prevent Hyper-V virtual machines from freezing or restarting unexpectedly, a problem that has primarily impacted Azure confidential VMs, which are engineered to safeguard data during processing.
The root cause of the issue stems from the management of memory paths through guest physical addresses (GPA), leading to potential VM lock-ups or random reboots. This situation jeopardizes system uptime and necessitates manual intervention for resolution.
To address this, Microsoft rolled out the KB5061977 update as an out-of-band release. This patch supersedes all previous updates and focuses on a specific flaw in the Hyper-V direct send path. Notably, the update particularly pertains to Azure confidential VMs and is not expected to affect standard Hyper-V installations, except in scenarios involving preview builds or testing environments.
For users affected by the Hyper-V freeze, the update cannot be accessed through the standard Windows Update process. Instead, administrators will need to manually download and install the standalone MSU package from the Microsoft Update Catalog.
This fix is timely, following a recent series of emergency patches released by Microsoft. Earlier in May, the company provided Hotpatch KB5061258 for Windows 11 LTSC 2024, and the release of KB5061977 comes on the heels of another update that introduced new features to Windows 11.
For further details on this fix, you can refer to the official Microsoft support page on KB5061977.