I'm having trouble installing the January 2026 Security Update (KB5073379) for Windows Server 2025 Standard on a physical server. Here's the issue: the update downloads and stages without a hitch, but when the system reboots to complete the installation, it fails during the post-reboot configuration stage. Windows informs me that something went wrong, and it's undoing the changes, which it does successfully. After about an hour, the server boots up normally. No blue screens or boot loops occur, and the rollback is clean each time.
I've already run some standard checks and fixes:
- DISM commands (CheckHealth, ScanHealth, RestoreHealth)
- SFC scan
- Reset Windows Update components
- Checked that the EFI/System Reserved partition has enough space (about 75% free)
- Verified there are no hardware or storage errors
- Only using Microsoft Defender, no third-party antivirus or EDR tools.
Interestingly, two other similar servers in the same environment managed to install the update without any problems. The servicing logs suggest the failure happens after the reboot, not during the staging process.
I'm seeking any advice: has anyone experienced this specific update failing on Server 2025? Are there any known issues with this CU or any further steps I should take apart from the typical DISM and SFC checks? Should I just wait for a superseding CU? Any insights would be appreciated!
3 Answers
Have you checked the exact error code that pops up during the failure? It could lead you to a specific issue. If it's `0x80073aa2`, that could point to a problem with the installation files, or a conflict with something on your server setup.
Event Viewer can provide some clues too. Make sure to check the logs under 'Windows Logs' ➔ 'Application' and 'System' for errors around the time of the installation attempt. It might shed light on what's failing during the post-reboot process.
If other servers are updating fine, it might just be a quirk with this specific machine. You could try installing the update in Safe Mode to rule out any software conflicts. If that doesn't work, it might be best to wait for a future cumulative update to avoid these issues.
Yeah, it seems like it’s failing during the installation phase but rolls back clean. Might want to scan through the logs thoroughly for anything that stands out.