Small-business IT teams can restore reliable File History backups by installing Microsoft’s latest Windows updates. Microsoft has fixed a September 2026 security-update issue that caused some systems to stop creating or updating backups, and the fix is available through optional cumulative updates for supported Windows 11 releases.
What happened
BleepingComputer reported that Microsoft fixed a known issue in which File History might fail to back up or restore files after the September 2026 security updates. Microsoft said the problem was fixed for Windows 11 customers in optional cumulative updates KB5124006 for Windows 11 26H1 and KB5124010 for Windows 11 24H2 and 25H2.
The issue could produce application crash events associated with FileHistory.exe and KERNELBASE.dll. Other symptoms included repeated “Reconnect your drive” alerts despite a connected, working drive, “No previous version available” messages for backed-up files, and a “Last Backup” timestamp that did not update.
Are you affected?
Microsoft identified systems running Windows 10 21H2 or later, Windows 10 Enterprise LTSC 2016 and 2019, and Windows 11 23H2 and later as potentially affected. Windows 11 26H1, 24H2, and 25H2 devices received the fix through KB5124006 or KB5124010, depending on the installed release.
IT teams can check for the problem by opening File History through Control Panel > System and Security > File History and reviewing the backup status. A connected drive may still produce a “Reconnect your drive” alert, while the “Last Backup” timestamp may fail to change. Event Viewer may also contain application crash entries referencing FileHistory.exe and KERNELBASE.dll.
The source and the official advisories do not provide a complete list of every affected Windows build or a separate version-checking command. Microsoft has confirmed the resolution for the named Windows 11 updates and has not stated in the cited material whether every affected Windows 10 configuration has received the fix.
What to do now
- Install the latest update available to the device. For affected Windows 11 releases, install KB5124006 on Windows 11 26H1 or KB5124010 on Windows 11 24H2 and 25H2. Microsoft recommends installing the latest update for the device.
- For systems that do not use optional updates, plan for the October 13 Patch Tuesday rollout. Microsoft said the fix would arrive with the next month’s Patch Tuesday updates if the optional updates were not installed.
- Verify File History after updating. Open Control Panel > System and Security > File History, confirm that the backup drive is connected, and check whether the “Last Backup” timestamp updates.
- Review Event Viewer for application crashes. Check for entries that reference FileHistory.exe and KERNELBASE.dll, particularly on systems that show drive reconnection alerts or cannot restore older file versions.
- Confirm that a usable backup exists before relying on File History for recovery. The feature automatically backs up account folders, including Documents, Music, Pictures, Videos, and Desktop, to an external drive or network location, but the reported issue can prevent new backups from being created or updated.
How File History works
File History was introduced in Windows 8 and later replaced by Windows Backup. It automatically backs up a user’s account profile folders to an external hard drive, such as a USB flash drive, or a network storage location. Users can then restore files that were deleted accidentally or damaged by using versions saved hours, days, or weeks earlier.
The September 2026 issue also affected other Windows areas. Microsoft released out-of-band updates for Hyper-V problems, Remote Desktop Services failures, and USB audio issues caused by the September Patch Tuesday security updates. It later provided a temporary fix for a separate bug that prevented some Windows 11 users from signing in with valid domain credentials after installing the same updates.
Microsoft’s release-health guidance for Windows 11 26H2 says administrators can check for updates through Settings > Windows Update > Check for Windows updates. The guidance also refers administrators to the Windows Updates API in Microsoft Graph for programmatic access to release-health information.
FAQ
Which Windows updates broke File History?
Microsoft said some File History users could not create or update backups after installing the September 2026 Windows security updates. The exact affected builds were not fully listed in the cited material.
How can I tell whether File History has stopped backing up?
Look for repeated “Reconnect your drive” alerts, a “Last Backup” timestamp that is not updating, “No previous version available” messages, and Event Viewer crash entries referencing FileHistory.exe and KERNELBASE.dll.
Which updates contain the File History fix?
Microsoft said KB5124006 for Windows 11 26H1 and KB5124010 for Windows 11 24H2 and 25H2 contain the fix. Devices that do not install the optional updates were due to receive it through the October 13 Patch Tuesday updates.