KB5078131: The OneDrive/Outlook Fix You Didn't Know Needed a Patch
Last week saw the release of an out-of-band update for Windows 10 Enterprise LTSC 2019 and Server 2019. Dubbed KB5078131 (OS Build 17763.8281), this patch finally addresses a persistent issue some users have been facing, namely, problems with cloud storage integration like OneDrive.
Why You Might Want to Pay Attention
After the rollout of KB5073723 on January 13th for many Windows versions, we heard reports from several users. They mentioned that opening or saving files directly in OneDrive often caused their app to freeze completely. Outlook wasn't immune either; particularly when configured to save its PST file on a network drive like OneDrive, it would sometimes stall during startup and refuse to reopen until people forced a reboot.
This latest update bundles fixes from two previous patches, KB5073723 and KB5077795. So if you're already running those older versions, installing KB5078131 will cover both updates in one go.
What the Patch Actually Does
KB5078131 tackles problems at different levels:
- For file handling issues generally impacting cloud storage communication, it replaces a problematic driver routine. This fix helps manage write-back caching properly when network connections experience delays or spikes.
- Regarding Outlook specifically, and the change is especially relevant if you keep your PST on OneDrive, the update includes protection against something called the "PST on OneDrive race condition." This issue was causing lockups during the startup of Outlook.
- And for data consistency, it resolves a timing glitch in Windows's cloud sync engine. That issue could lead to orphaned temporary files and potentially cause emails to seemingly disappear or re-sync unexpectedly.
Checking If You Need It
To find out if this update applies to you:
- Open Settings and select About.
- Check your OS build number. If it's still showing 17763.8280 or earlier, KB5078131 is waiting for installation.
Installing Manually
For systems not receiving automatic pushes (or perhaps running a server where that might vary):
- Go to the official Microsoft Update Catalog website.
- Search specifically for 'KB5078131.'
- Download the .msu file suited for Windows 10 Enterprise LTSC or Server and matching your system's x64 architecture.
Once downloaded, double-click the installer; it should automatically handle any necessary dependencies. You don't necessarily need to reboot straight away after installation if things are quiet, but giving your PC a restart afterward is recommended. It helps clear caches for services that might use cloud storage temporarily.
For more information, check out the Microsoft support article below:
January 24, 2026—KB5078131 (OS Build 17763.8281) Out-of-band - Microsoft Support
January 24, 2026—KB5078131 (OS Build 17763.8281) Out-of-band - Microsoft Support
