Windows VM Server 2025 consistently fails to install the June security update KB5094125.

The error codes indicate Windows Update component issues on the Windows Server 2025 VM. Use the supported servicing/reset steps and then reinstall the update.

Because this is an Azure VM, back up the OS disk or take a VM snapshot before making changes.

1. Cleanly reset Windows Update components
   Run these commands in an elevated Command Prompt inside the VM to reset the SoftwareDistribution and Catroot2 folders (similar to what was already tried, but in the documented order):

net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver

ren C:\Windows\SoftwareDistribution C:\Windows\SoftwareDistribution.old
ren C:\Windows\System32\catroot2 C:\Windows\System32\catroot2.old

net start wuauserv
net start cryptSvc
net start bits
net start msiserver

This clears the Windows Update data store and download cache, which can fix 0x8007066A/0x800f0991 when they are caused by corrupted update metadata or payload.

2. Repair possible system corruption
   If the update still fails, repair the servicing stack and system files:

DISM /Online /Cleanup-Image /RestoreHealth
SFC /Scannow

Run DISM first, then SFC. If either reports corruption that is repaired, restart the VM and try installing KB5094125 again.

3. Use Azure VM Windows Update tools (Azure VMs only)
   For Azure VMs, run the public troubleshooting tools to detect and reset Windows Update issues before contacting support:

• Azure VM Windows Update Error Detection Tool
• Azure VM Windows Update Reset Tool

These tools diagnose specific Windows Update errors and reset the Windows servicing stack for Azure VMs.

4. If the update still fails
   If KB5094125 continues to fail after:

• Resetting SoftwareDistribution and Catroot2, and
• Running DISM/SFC, and
• Using the Azure VM Windows Update tools,

then open a case with Microsoft Support for deeper analysis of CBS.log and WindowsUpdate.log from the VM. Persistent 0x800f0991 after a full reset and repair typically requires detailed log review.

References:

• Troubleshoot Windows Update error 0x80070490
• Prepare to deploy Windows
• Windows Update - additional resources
• Troubleshoot OS startup – Windows Update installation capacity