ALGC News — A significant disruption to data recovery workflows in Windows 11 has been addressed following the release of a targeted optional update. For many technical users and system administrators, the September 2026 security patches introduced a critical flaw that rendered the File History feature inoperable. This article details the technical specifics of the bug, the confirmed fix, and the necessary steps to restore backup integrity on affected systems.
The Impact of the September 2026 Security Update
Following the installation of the latest security patches, a widespread issue emerged where the File History utility failed to create or update backups. File History is a fundamental component of Windows data protection, designed to automatically save copies of user files. By default, it monitors folders within the user profile, including Documents, Music, Pictures, Videos, and the Desktop. These backups are typically directed to an external USB drive or a Network Attached Storage (NAS) device, providing a safety net against accidental deletion or file corruption.
The bug manifested in several distinct ways that frustrated users relying on version control for their personal and professional files. Affected devices began displaying a persistent “Reconnect your drive” message, even when a compatible and functional backup drive was physically connected and recognized by the system. Furthermore, the “Last Backup” timestamp stopped updating, giving users a false sense of security regarding their data protection status. In more severe cases, previously backed-up files became inaccessible, displaying the error “No previous version available.” This effectively locked users out of their historical data, making recovery of deleted or corrupted files impossible until the issue was resolved.
Technical Diagnosis and Scope of the Issue
Microsoft confirmed that the root cause of this failure was a bug introduced by the September 2026 security update. The scope of the issue was extensive, affecting all current versions of Windows 10 and Windows 11. This included major releases such as 21H2, 22H2, 23H2, 24H2, 25H2, and the newer 26H1 build. For IT professionals, the breadth of this impact meant that nearly every modern Windows deployment was potentially vulnerable to data loss if File History was configured as a primary recovery mechanism.
System logs provided further insight into the nature of the crash. In many instances, the Event Viewer recorded application crash events referencing FileHistory.exe and KERNELBASE.dll. These specific references indicated a low-level conflict between the backup service and the kernel base library, likely triggered by changes in the security patch. This technical detail was crucial for diagnosing the problem, as it pointed to a system-level incompatibility rather than a simple configuration error or hardware failure.
The Official Fix: Optional Updates KB5124010 and KB5124006
Microsoft has since released a fix for this known issue through optional updates. For users running Windows 11 25H2 and 24H2, the solution is available via update KB5124010. For those on the Windows 11 26H1 build, the fix is contained in update KB5124006. These updates specifically address the failure to back up or restore files to external drives or network locations, resolving the erroneous “Reconnect your drive” prompts and restoring the functionality of the “Last Backup” timestamp.
It is important to note that these updates are not installed automatically by default. They are classified as optional updates, meaning users must manually initiate the installation process. To apply the fix, users should navigate to Windows Settings, select Windows Update, and then choose Advanced options. From there, selecting Optional updates will reveal the relevant security and quality updates. Installing the appropriate KB number will resolve the File History bug immediately.
Interim Solutions and Future Rollouts
For users who are unable or unwilling to install the optional updates immediately, Microsoft previously advised rolling back the problematic September security update. This process involves uninstalling the specific security patch that introduced the bug, which restores File History to its previous working state. However, this is a temporary measure, as the system will remain vulnerable to other security threats addressed by the September patch until the official fix is applied.
If the optional updates are not installed manually, the fix is scheduled to roll out as part of the standard October Patch Tuesday release. This means that users who ignore the optional update notification will continue to experience the File History bug for approximately one month. Given the critical nature of data backup, it is recommended to install the optional update as soon as possible to ensure continuous protection of user data.
Conclusion
The resolution of the Windows 11 File History bug highlights the importance of monitoring optional updates, particularly those addressing critical data management features. While the initial security patch caused significant disruption, the prompt release of KB5124010 and KB5124006 provides a clear path to recovery. Users should verify their Windows version and install the corresponding update to restore full backup functionality. For technical readers, this incident serves as a reminder to maintain independent backup strategies, such as third-party imaging tools, to mitigate risks associated with OS-level update failures.