Microsoft Warns September 2026 Windows Update May Break File History Backups
Microsoft has warned that the built-in File History backup feature in Windows may stop working on some systems after users install the September 2026 security update.
Windows File History backups may fail after September update
File History, introduced for Windows 8, replaced Windows Backup and automatically saves copies of files. Users can recover files that were accidentally deleted or corrupted by restoring older versions from hours, days, or weeks earlier.
By default, File History backs up folders in a user’s account profile, including Documents, Music, Pictures, Videos, and Desktop. Backups can be stored on an external drive, such as a USB flash drive, or on network-attached storage (NAS).
The issue, identified by BleepingComputer and first discovered by Microsoft MVP Susan Bradley, can cause affected systems to record application crash events for FileHistory.exe and KERNELBASE.dll in Event Viewer, according to Microsoft’s service alert.
“After installing the September 2026 Windows Security Updates (original KB above), some customers using File History may be unable to create or update backups,” Microsoft said. “File History, available from Control Panel > System and Security > File History, is used to back up files to external drives or network locations.”
Symptoms of the Windows File History bug
On affected devices, Windows may incorrectly display a “Please reconnect the drive” message even when a compatible backup drive is connected and working properly.
Other reported symptoms include:
- The Last Backup timestamp does not update.
- Previously backed-up files show “No previous versions.”
- File History fails to create or update backups.
- FileHistory.exe and KERNELBASE.dll crash events appear in Event Viewer.
Affected Windows versions
Microsoft said the File History issue affects the following Windows releases:
- Windows 10 version 21H2 and later
- Windows 10 Enterprise LTSC 2016
- Windows 10 Enterprise LTSC 2019
- Windows 11 version 23H2 and later
September 2026 Windows update causes additional problems
The September 2026 cumulative update is linked to multiple issues affecting home and business Windows users.
A week ago, Microsoft released an out-of-band update to address an outage affecting Remote Desktop Services. The company has also documented Hyper-V issues and USB audio problems caused by this month’s security updates.
However, the emergency updates did not resolve every audio issue introduced by the September 2026 update. Microsoft said it is still working on fixes for the remaining problems.
Microsoft also shared a temporary workaround for another bug that prevents some Windows 11 users from signing in with valid domain credentials after installing the September update.
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Source: www.bleepingcomputer.com