- Microsoft issues an urgent out-of-band (OOB) fix for problems with creating Hyper-V virtual machines.
- The problem only impacts virtual machines using Software Defined Networking managed by System Center Virtual Machine Manager.
- The out-of-band patch of December 20th will not be installed automatically through Microsoft Update and has to be obtained manually.
Last week, Microsoft has announced that the latest December Patch Tuesday updates for Windows Server caused problems while creating virtual machines on Hyper-V hosts. In order to fix this problem that prevented the creation of virtual machines (VMs) on Hyper-V hosts, Microsoft has published emergency out-of-band (OOB) Windows Server updates.
Emergency OOB update for Hyper-V VM issues
The problem only impacts VMs using Software Defined Networking (SDN) and managed by System Center Virtual Machine Manager (SCVMM). Only Windows Server 2019 and Windows Server 2022 instances are impacted after installing December 2022 Patch Tuesday updates (KB5021237 and KB5021249).
Administrators should update all affected Hyper-V hosts in their environment with the OOB cumulative updates provided today in order to fix this problem. Microsoft stated that you don’t need to update any other servers or client devices in your environment to fix this issue.
Will not be installed automatically
Mentioned updates will not be obtained through Windows Update and will not be automatically installed on Windows Server instances that were affected. You must look up the KB number in the Microsoft Update Catalog, download the files, then manually install them.
The list of emergency Windows Server cumulative updates released today includes:
Temporary fix available
A temporary fix is available for admins who cannot immediately install the updates on affected SDN-based SCVMM deployments.
This workaround requires running a set of commands on all SCVMM-managed Hyper-V hosts from an elevated PowerShell window, immediately after installing the KB5021237 and KB5021249 updates. You can find scripts for large-scale deployments and further details here.