Microsoft fixes Hyper-V VM problem caused by Patch Tuesday

Microsoft has pushed out an emergency fix for a problem in Windows Server caused by patch updates that made it impossible for some organizations to create virtual machines on Hyper-V hosts.

The issue arose after Windows Server 2019 and Windows Server 2022 users installed two updates that were part of this month's Patch Tuesday releases. Some found they were unable to create VMs for hosts that are managed by System Center Virtual Machine Manager (SCVMM) and leverage software-defined networking (SDN) technologies.

Microsoft engineers initially created a workaround for enterprises and a week later have issued an out-of-band (OOB) fix that users can apply to all of their Hyper-V systems that are using SDN and SCVMM that will fix issues across the network.

"You do not need to install any update or make any changes to other servers or client devices in your environment to resolve this issue," Microsoft wrote in its Windows Health Dashboard.

The problem arose after users installed the KB5021249 and KB5021237 updates on Windows Server or Azure Stack HCI hosts. When trying to create a new VM or network adapter on an existing, some users failed to get network connections, SDN software load balancers or SDN gateway services.

Initially Microsoft offered them a workaround that involved using an elevated PowerShell window on the affected hosts. Now organizations can get a standalone package for the OOB updates by searching for the KB update number in the Microsoft Update Catalog and manually import them into Windows Server Update Services (WSUS), with instructions found here, and Endpoint Configuration Manager (with instructions here).

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Customers will have to manually install the updates, which will not install automatically. The cumulative update for Windows Server 2019 is KB5022554; for Windows Server 2022, it's KB5022553.

"You do not need to apply any previous update before installing these cumulative updates," Microsoft wrote. "If you have already installed updates released December 13, 2022, you do not need to uninstall the affected updates before installing any later updates including the updates listed."

The Patch Tuesday updates have been causing a few headaches for Windows users. Earlier this week, Microsoft warned that one of the cumulative updates – KB5021233 – that some people using various versions of Windows 10 systems were running into the dreaded Blue Screen of Death when starting up the operating system.

The software vendor said it is working on a fix for the problem and, in the interim, rolled out a workaround. ®