Microsoft Fixes Windows Update Failures Linked to WUSA Installer

Microsoft fixes Windows Update failures linked to WUSA installer

OverviewMicrosoft has resolved a long-standing issue that caused Windows updates released since May 2025 to fail when installed via the Windows Update Standalone Installer (WUSA) from a network share. WUSA is a built-in Windows command-line tool used by administrators to install or remove patches packaged as .msu files through the Windows Update Agent API. The problem primarily affected enterprise networks running Windows 11 24H2/25H2 and Windows Server 2025, where WUSA installations from network shares containing multiple .msu files could fail with errors such as ERRORBADPATHNAME. The bug did not appear when a single .msu file was involved or when files were stored locally.

What happened and who was affected

• The issue arose when updates released on or after May 28, 2025 (KB5058499) were installed using WUSA from network shares that contained more than one .msu file.
• Home devices were largely unaffected because WUSA is not commonly used for updates there; the problem was more visible on enterprise networks and devices using Windows Update with WUSA from network locations.
• Affected scenarios included installations initiated by WUSA or by double-clicking a .msu file on a network share with multiple .msu files.
• Microsoft confirmed the behavior and noted that it did not occur when updating a single .msu file or when the files were local to the device.

Key milestones and mitigations

• August 2025: Microsoft acknowledged the issue publicly, outlining the ERRORBADPATHNAME problem when using WUSA from network shares with multiple .msu files. The bug was associated with updates released May 28, 2025 and later.
• September 2025: A Known Issue Rollback Group Policy was deployed automatically for home and non-managed devices, providing a workaround to mitigate the impact on those environments.
• June 2026: The issue was officially fixed in the June 2026 Patch Tuesday updates for both Windows 11 24H2/25H2 and Windows Server 2025.

The fix

• Windows 11 24H2/25H2: KB5079391
• Windows Server 2025: KB5094125

What to know about the fix

• The June 2026 cumulative updates address the root cause for all affected systems.
• If you installed an update prior to this fix and still encounter issues, you can continue to use the workaround of saving the .msu files locally on the device and installing from that local location.
• After restarting Windows following an .msu installation via WUSA, it may be necessary to wait about 15 minutes before checking the Update History page in Settings. This delay helps ensure that the Update History reflects a successful installation accurately.

Context and related issues

• Microsoft has previously addressed other update-related problems, including fixes for 0x80240069 errors that affected Windows 11 updates in 2025 and related enterprise deployment challenges.
• There were also notes about issues when upgrading to Windows 11 24H2 or 25H2 and how some devices encountered problems with monthly security updates, as well as broader warning about update installation on upgraded PCs.
• While the WUSA-from-network-share issue was specific in scope, the broader update ecosystem remains sensitive to how patches are delivered—especially in enterprise environments that rely on network shares and centralized deployment tools.

Technical essentials

• WUSA (Windows Update Standalone Installer) enables installation of .msu updates via the Windows Update Agent API.
• The problem surfaced when multiple .msu files resided on a network share, complicating path resolution or file handling during installation.
• A single .msu or locally stored files did not trigger this failure mode, highlighting the importance of deployment method in update reliability.
• The June 2026 fixes align with a broader strategy to stabilize update delivery on managed networks while preserving the integrity of cumulative updates for Windows 11 and Windows Server 2025.

Impact assessment

• Enterprises relying on network-based deployment through WUSA should verify that devices receive the June 2026 updates (KB5079391 for Windows 11 24H2/25H2 and KB5094125 for Windows Server 2025).
• For legacy or isolated environments without automatic patch rollback policies, the local-file installation workaround remains a viable interim path until updates are fully rolled out.
• Post-installation verification steps may require a short waiting period before Update History reflects success, to avoid confusion during audits or change-control reviews.

Related considerations

• The evolution of update delivery continues to emphasize reliability when deploying patches across complex networks.
• Ongoing monitoring and health dashboards from Microsoft provide guidance on the status of known issues and their resolutions, particularly for environments with automated deployment pipelines and network shares.

In summary, the June 2026 Patch Tuesday marks the resolution of a longstanding Windows Update failure linked to the Windows Update Standalone Installer when used from network shares containing multiple .msu files. The fix covers Windows 11 24H2/25H2 and Windows Server 2025, with documented workarounds preserved for scenarios where updates were deployed prior to the fix.