Windows 11 KB5079391 fixes year-long WUSA network installation bug

Microsoft says a long-running Windows 11 update-installation bug tied to the Windows Update Standalone Installer is now resolved. The company says devices affected by the issue can be fixed by updates released on March 24, 2026, and later, specifically naming KB5079391. The bug could cause updates to fail with ERROR_BAD_PATHNAME when admins tried to install .msu packages from a network share containing multiple .msu files.

This was mainly an enterprise-facing problem rather than a typical home-user one. Microsoft says WUSA is generally used in managed environments, and the failure did not occur when only one .msu file was present in the shared folder or when the update files were stored locally on the device.

KB5079391 is the official fix

Microsoft’s support pages now list KB5079391 as a March 26, 2026, preview update for Windows 11 versions 24H2 and 25H2, carrying OS Builds 26100.8116 and 26200.8116. In the release health documentation, Microsoft says the shared-folder WUSA issue was formally marked resolved on March 26, while the fix itself was delivered by updates released March 24 and later.

The issue had been around since 2025

Microsoft traces the problem back to devices that had installed updates released on May 28, 2025, starting with KB5058499. In affected environments, installs could fail both when a user double-clicked a .msu file from a network share and when WUSA was used directly against that same share. Microsoft had already pushed a Known Issue Rollback beginning in September 2025 for most home users and non-managed business devices, while IT admins could also use a dedicated Group Policy to address affected managed systems.

Microsoft states devices already running the update released March 24, 2026, or later do not need a workaround. Systems still on older builds can avoid the issue by copying the .msu files to local storage before installing them. The company also notes that after a WUSA-based install, Settings may temporarily continue to show that a restart is required even when the update has already completed, though that status should clear on its own.