The Update BureauKB5078131: Cumulative update for Windows Server, version 2019, January 2026. Cloud-file errors and Outlook hangs fixed
Fixes file access problems that could leave some apps unresponsive and cause Outlook to hang when PST files are stored on OneDrive.
Does it affect you? Applies to: Devices running Windows Server 2019.
Review notes Additional details from the official release notes (2) Read notes
- Known issues The official page titles this issue as Japanese characters failing to render correctly in PowerShell, but its symptom section describes intermittent file-operation failures in some 32-bit apps. The page says the issue is resolved in updates released on and after April 14, 2026, such as KB5082123.
- Known issues The file-operation issue applies to 32-bit apps that are large address aware and use the CopyFile API. The page says 64-bit apps and apps that are not large address aware are not affected.
The official sources are linked at the end of the page.
Microsoft publishes separate notes for this KB for Windows 10.
What changes
Fix 1 change
File System
For: Devices using cloud-based storage
-
Some apps can open or save files in cloud storage again without becoming unresponsive. In certain Outlook setups, PST files stored on OneDrive no longer cause Outlook to hang, and the related missing or re-downloaded email symptoms are addressed.1
Addresses problems that began after Windows updates released on and after January 13, 2026, when opening or saving files in cloud storage such as OneDrive or Dropbox.
Improvement 1 change
Servicing stack
-
The component that installs Windows updates receives quality improvements.2
Includes servicing stack update KB5074222, build 17763.8260.
Known issues
-
Japanese characters fail to render correctly in PowerShell
Some 32-bit apps can intermittently fail to save, copy, or attach files; 32-bit Word or Excel might show “Document not saved.” The issue is more likely when commercial or enterprise security software uses extended file attributes, and is unlikely on home or unmanaged commercial devices. KB5082123 resolves it.3
Resolution Fixed in KB5082123Install KB5082123 (or a later cumulative update) on affected devices. No manual workaround is required after updating.
-
Some devices with Virtual Secure Mode enabled might fail to shut down or hibernate
Some Secure Launch-capable PCs with Virtual Secure Mode enabled might restart instead of shutting down or entering hibernation. KB5075904 addresses this issue.4
Resolution Fixed in KB5075904Install KB5075904 (or a later cumulative update) on affected devices. No manual workaround is required after updating.
Technical details
Data sheet · Security · Downloads · Components Click to collapse or expand
Data sheet
- Released
- 2026-01-24
- Classification
- Updates
- Type
- Cumulative update
- Restart
- Required
- Replaces
- KB5077795, KB5073723, KB5074975, KB5071544
- Replaced by
- KB5075904
| Version | Build | Channel |
|---|---|---|
| 2019 | 17763.8281 | General availability |
Security
No vulnerabilities are listed for this update.
Downloads (Microsoft Update Catalog)
Updated components
14 files changed since the previous update for the same versions.
Sources
Cited passages from Microsoft's official notes (4)
-
1.
Fixed: After installing the Windows update released on and after January 13, 2026, some applications became unresponsive or encountered unexpected errors when opening files from or saving files to cloud-based storage, such as OneDrive or Dropbox.
support.microsoft.com -
2.
This update makes quality improvements to the servicing stack, which is the component that installs Windows updates.
support.microsoft.com -
3.
You might have intermittent issues saving, copying, or attaching files using 32-bit apps, which are large address aware and using the CopyFile API.
support.microsoft.com -
4.
This issue is addressed in KB5075904.
support.microsoft.com
Checked automatically: 8 of 8 checks passed, 4 quoted passages · compared with Microsoft's page on Sep 25, 2026
- Quotes found in the official pages: passed
- Numbers found in the sources: passed
- Vulnerabilities from the dossier only: passed
- Links to allowed domains only: passed
- Every official change covered: passed
- Readable plain text: passed
- Changes confirmed by the file list: passed
- Sources agree: passed
A second AI read the text against the sources: correctness 3/5, clarity 4/5, completeness 3/5. How we work
Published by The Update Bureau. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake