Fixing Hyper‑V VM Freezes Error in Windows Server After 2025 Update

If you're running Hyper‑V on Windows Server 2022 and recently updated your system, you might have noticed this: " Virtual Machines freeze randomly or go into restart loops after the May or April 2025 Windows Update.”

WINDOWS SERVER

8/6/20252 min read

Yes — this was a real and widespread issue. And Microsoft acknowledged it.

What was the cause of the problem?

After the May 2025 Cumulative Update (example KB: KB5037780), many admins reported:

  • VMs freezing during boot or while running.

  • Checkpoint and backup operations failing.

  • VMs going into restart loops.

  • Event Viewer logs showing critical hypervisor errors.

Root Cause

The issue was traced to a bug in Hyper‑V integration components, introduced by a recent patch. Microsoft’s May 2025 update accidentally disrupted VM state handling, especially when:

  • Using dynamic memory

  • Running Windows Server guests

  • Backups or checkpointing via VSS were triggered

Step-by-Step Fix

Step 1: Confirm If Your Server Is Affected

  • Go to Control Panel → Windows Update → View update history

  • Look for updates from May 2025 or April 2025, such as:

    • KB5037780

    • KB5036893

Step 2: Install Microsoft’s Emergency Fix

(Out-of-Band Patch)

In late May 2025, Microsoft released a fix specifically for this Hyper‑V bug.

Option A – Automatic Install

  • Open Settings → Windows Update

  • Click Check for Updates

  • Install the June 2025 Hyper-V fix (KB5039002 or latest)

Option B – Manual Install

  • Go to the Microsoft Update Catalog

  • Search for:
    > KB5039002 or “Hyper-V patch June 2025”

  • Download the correct .msu file for your version

  • Install → Reboot

If you're still facing the issue, go with the next options.

Step 3: Restart Hyper‑V Services

After patching, it’s safe to restart the Hyper‑V host. But if needed manually:

  • open powershell

  • You can also restart from Hyper‑V Manager.

Step 4: Disable Dynamic Memory

If patching isn’t an option right away, disable Dynamic Memory on affected VMs:

  • Open Hyper‑V Manager

  • Right-click the VM → Settings

  • Go to Memory

  • Uncheck Enable Dynamic Memory

  • Allocate a fixed memory value (e.g., 4 GB)

How to Verify Everything Works

After installing the patch and rebooting:

  • Boot up all VMs

  • Run heavy workloads or simulate backups/checkpoints

  • Watch logs for 10–15 minutes