Microsoft offers an emergency solution to Windows Server HyperV VM problems

Microsoft released an emergency out-of band (OOB), Windows Server update to fix a known problem that was preventing Hyper-V hosts from creating virtual machines (VMs) after this month’s Patch Tuesday Updates.

This issue only affects VMs that are managed using the System Center Virtual Machine Manager, (SCVMM), and Software Define Networking (SDN).

Windows administrators who are affected by the problem see warnings about live migrations, SLB Load Balancing or SDN RAS Gateway failures, as well as problems when attaching Virtual Network Interface Cards to VMs.

After installing the December 2022 Patch Tuesday update , and , Windows Server 2019 or Windows Server 2022 shouldn’t be affected.

Administrators should install OOB cumulative updates today on affected Hyper-V hosts to resolve the issue.

Microsoft explained.

Windows Update does not deliver OOB updates

The updates for today are not available through Windows Updates. They will not be installed automatically on affected servers.

You will need to look for the KB number within the and download the files. Then, manually install the package.

These files can be imported manually into Windows Server Update Services, (WSUS), and Microsoft Endpoint Configuration Manager.

Microsoft provides additional instructions for how to import updates from Microsoft Update Catalog into or .

Today’s Windows Server emergency cumulative updates include:

Redmond said today that you don’t need to install any prior update in order to receive these cumulative updates.

You don’t need to remove any updates you already have installed, such as the December 13th 2022 updates.

to admins that are unable to immediately install the latest updates for affected SDN-based SCVMMM deployments.

You can use this workaround to run a series of commands from an elevated PowerShell Window on SCVMM-managed Hyper-V host hosts (immediately following installation of the KB5021237 or KB5021249 update).

The SCVMM Management Server has scripts that can be used for large-scale deployments. For more information on .