Microsoft warns September 2026 updates can break File History backups

Microsoft has warned that the September 2026 security updates may prevent the built-in File History feature from creating or updating backups on some Windows systems.

File History, introduced in Windows 8, automatically saves copies of files so users can recover files deleted or damaged hours, days, or weeks earlier. By default, it backs up folders including Documents, Music, Pictures, Videos, and Desktop to an external drive or network storage location (NAS).

According to a Microsoft service alert seen by BleepingComputer, affected customers may see application crash events for FileHistory.exe and KERNELBASE.dll in Event Viewer. Windows may also show incorrect “Reconnect your drive” messages even when a compatible drive is connected and working.

• The “Last Backup” timestamp may stop updating.
• Previously backed-up files may show “No previous version available.”
• File History may be unable to create or update backups.

The affected releases include Windows 10 21H2 or later, Windows 10 Enterprise LTSC 2016 and 2019, and Windows 11 23H2 or later. Microsoft has not announced a fix in the supplied alert.