Microsoft Fixes WUSA Installer Bug Breaking Windows Updates on Network Shares
Microsoft has resolved a long-standing known issue that caused Windows updates released since May 2025 to fail when deployed via the Windows Update Standalone Installer (WUSA) from a network share. WUSA is a built-in command-line utility that allows administrators to install or remove Microsoft Standalone Update (.msu) files through the Windows Update Agent API, making it a common tool in enterprise environments. The bug specifically affected Windows 11 24H2/25H2 and Windows Server 2025 systems on enterprise networks, producing an ERROR_BAD_PATHNAME error when multiple .msu files were present in the network share. The issue did not occur when installing a single .msu file or when files were stored locally on the device.
Microsoft first acknowledged the problem in August 2025 and deployed an automatic Known Issue Rollback via Group Policy for home and non-managed business devices starting in September 2025. The full fix arrived as part of the June 2026 Patch Tuesday, shipped through cumulative updates KB5079391 for Windows 11 and KB5094125 for Windows Server 2025. As a temporary workaround, Microsoft advised administrators to copy .msu files to a local path before installation and wait at least 15 minutes after reboot before verifying success in the Settings app's Update History page.
This is the third update-deployment bug Microsoft has addressed in the past year. In April 2025, the company resolved a Windows Server Update Services (WSUS) failure blocking April 2025 security updates for enterprise customers, followed by an identical error causing August 2025 Windows 11 updates to fail with 0x80240069 code. IT teams managing update distribution over SMB can validate the underlying connectivity and signing of their file shares with our port scanner to confirm ports 445 and 139 are properly configured, and verify transport-layer protections with the SSL/TLS checker. Earlier this week, Microsoft also separately warned that some Windows 11 24H2/25H2 devices may experience failures when installing the latest monthly cumulative updates.