CybersecurityVulnerability Management

Microsoft Fixes File History Backup Bug in Windows Updates

Analyst 207||Source: BleepingComputer
Cluttered home office desk with laptop, external hard drive, and scattered papers in soft natural daylight.
"After installing the September 2026 Windows security update [..], some customers using File History, might be unable to create or update backups," Microsoft said.

What broke: File History stopped making or restoring backups

Microsoft identified a known issue in its September 2026 security updates that broke the built-in File History backup feature on some Windows installations. File History — which the company notes was replaced by Windows Backup — backs up a user’s account profile folders (Documents, Music, Pictures, Videos and Desktop) to an external hard drive or a network storage location, then allows recovery of older file versions.

On impacted systems, users saw application crash events in Event Viewer referencing FileHistory.exe and KERNELBASE.dll. Other reported symptoms included repeated "Reconnect your drive" alerts even when compatible backup drives were connected, previously backed-up files showing "No previous version available," and the "Last Backup" timestamp failing to update.

Which Windows builds reported problems

Microsoft listed the affected builds as Windows 10 21H2 or later, Windows 10 Enterprise LTSC 2016/2019, and Windows 11 23H2 and later. The break affected creating and updating File History backups to both external drives and network locations.

How Microsoft fixed it and how users get the fix

Microsoft said on Tuesday that the known issue has been fixed in a September 2026 preview update. "This update addresses an issue where File History might fail to back up or restore files to an external drive or network location," Microsoft said, and recommended installing the latest update because it "contains important improvements and issue resolutions, including this one."

For users who do not want to install optional preview updates, Microsoft said the fix will be included in the next monthly Patch Tuesday, scheduled to roll out on October 13.

Related patches Microsoft has issued in September 2026

The File History fix arrived amid a string of recent out-of-band patches. One week earlier Microsoft released out-of-band updates to address Hyper-V problems, Remote Desktop Services failures, and USB audio issues that were triggered by the September Patch Tuesday security updates. Days after those releases it also provided a temporary fix for a bug that prevented some Windows 11 users from logging in with valid domain credentials following the same September updates.

How end users, enterprises, and technologists will respond

  • End users: Those seeing "Reconnect your drive" alerts, "No previous version available" messages, or a stale "Last Backup" timestamp will either install the September preview update Microsoft published or wait for the October 13 Patch Tuesday to receive the correction automatically.
  • Enterprises and IT teams: Administrators responsible for Windows 10 21H2+, Windows 10 Enterprise LTSC 2016/2019, or Windows 11 23H2+ deployments must weigh deploying the optional preview update now against waiting for the October cumulative rollout, while also accounting for other recent out-of-band fixes that changed Hyper-V, RDS, USB audio, and domain login behavior.
  • Technologists and support teams: The Event Viewer crash signatures referencing FileHistory.exe and KERNELBASE.dll are concrete diagnostics to check when triaging reports of failed backups or restore attempts.

Conclusion

Microsoft has acknowledged and fixed a File History failure caused by the September 2026 security updates and has pushed the correction into a September preview update, with the fix scheduled for inclusion on Patch Tuesday, October 13, for those who skip optional updates. Users experiencing the specific File History symptoms described by Microsoft should either apply the preview update or plan to receive the patch on October 13, and administrators should factor the timing of that patch into their rollout and testing schedules — especially given the cluster of other fixes Microsoft has issued in recent weeks.

Original reporting: BleepingComputer — Microsoft fixes Windows backup feature broken by September updates

Emerging ThreatsMicrosoftWindowsWindows UpdatesFile History BackupBackup Bug
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