A forthcoming Windows update in September 2026 could disrupt File History backups for some users, sparking warnings and potential data recovery issues amidst ongoing patch cycle problems.
Microsoft has warned that September 2026 security updates may disrupt File History on some Windows PCs, leaving the built-in backup tool unable to create or refresh copies of users’ files. According to a service alert first highlighted by Microsoft MVP Susan Bradley and seen by BleepingComputer, affected systems can log crashes involving FileHistory.exe and KERNELBASE.dll.
File History is the older Windows backup option that stores copies of personal files from folders such as Documents, Music, Pictures, Videos and Desktop on an external drive or network location. Microsoft said some users may see a misleading “Reconnect your drive” message even when a compatible backup device is attached and working normally. Other signs include the “Last Backup” field failing to advance and older versions of files showing “No previous version available”.
The problem affects Windows 10 21H2 and later, including Enterprise LTSC 2016 and 2019 editions, as well as Windows 11 23H2 and newer. The originating updates listed by Microsoft include KB5124012 for Windows 11 version 26H1, KB5124008 for Windows 11 versions 25H2 and 24H2, KB5122880 for Windows 11 23H2, KB5122878 for Windows 10 22H2 and 21H2, KB5122876 for Windows 10 Enterprise LTSC 2019, and KB5123099 for Windows 10 Enterprise LTSC 2016.
The File History fault adds to a wider run of problems linked to the September patch cycle. Microsoft has already pushed out-of-band fixes for separate failures affecting Remote Desktop Services, Hyper-V and USB audio, although it said some audio issues remain unresolved. It has also provided a temporary workaround for another bug that can stop some Windows 11 users from signing in with valid domain credentials after installing the same updates.
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