Win Update KB5129194 Windows 11 Out-of-band Cumulative Update build 28000.2956 (26H1) - Sept. 14

This out-of-band update for Windows 11, version 26H1 (KB5129194) includes the latest fixes and improvements. Visit the Windows release health dashboard for the latest status on this release.

Improvements​

This out-of-band update includes the following improvements:

• [Security] This update includes protections documented in CVE-2026-62721, which refers to a Windows User-Mode Power Service (UMPS) Elevation of Privilege vulnerability.
• [Remote Desktop Services (known issue)] Fixed: This update addresses an issue affecting Remote Desktop Services (RDS) after installing the September 2026 Windows security update (KB5124012). In affected environments, RDS might become unstable, causing RDP connection and sign-in failures or servers to become unresponsive during Remote Desktop configuration. Related tools, including Microsoft Management Console (MMC), RDS Licensing Diagnoser, File Explorer, and the Windows Update page, might also stop responding.
• [Hyper-V (known issue)] Fixed: Some applications that use HCS-managed virtual machines experienced issues when sharing host folder with Linux VMs using Plan9. Folders shared from the Windows host using Plan9 did not appear or could not be accessed in the guest environment.
• [8-channel or 3D audio modes] Fixed: Some USB Audio Class 1.0 devices functioning as expected in standard stereo configurations failed when using multichannel audio features, including 8-channel or 3D audio modes. (Note: There are other audio symptoms not resolved in this OOB update. See the “Known issues in this update” section for more information.)

If you've already installed previous updates, your device will download and install only the new updates included in this package.

Component updates​

AI components
This release updates the following AI components to version 1.2608.951.0: Image Search, Content Extraction, Semantic Analysis, and Settings Model.

To learn more, see Release information for AI components.

Servicing stack updateIncludes KB5125104 (Build 28000.2950), which improves the reliability of the Windows update installation process.

Known issues in this update​

How to get this update​

Before you install this update​

Microsoft combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). For general information about SSUs, see Servicing stack updates.

Deployment​

If you deploy dynamic updates such as this update to an existing Windows image, ensure the boot.stl file is included as part of the installation media. Failure to include the file might prevent devices from successfully starting from the installation media and can result in error code 0xc0430001.

Note: The boot.stl file is used during Secure Boot validation and must match the Windows version and architecture of the image you are updating.
To ensure the boot.stl file is included as part of the installation media, do one of the following:

• Use the Update WinPE script to update an existing Windows image. (Recommended)
• Manually copy the boot.stl file from the device Windows\Boot\EFI folder to the corresponding folder on your installation media before deploying the update.

For information about how to apply Dynamic Update packages to existing Windows images, see Update Windows installation media with Dynamic Update.

Install this update​

To install this out-of-band update, use one of the following Windows and Microsoft release channels.

File information​

For a list of the files provided in this update, download the file information for out-of-band update KB5129194.

For a list of the files provided in the servicing stack update, download the file information for the SSU (KB5125104) - version 28000.2950.





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