August 11, 2026—KB5120249 (OS Builds 19045.7663 and 19044.7663)

Applies To
Windows 10 ESU Windows 10 Enterprise LTSC 2021 Windows 10 IoT Enterprise LTSC 2021

Windows Secure Boot certificate expiration

Important Secure Boot certificates used by most Windows devices started to expire in June 2026. Microsoft has been updating these certificates on PCs and non-managed business devices for the past months. Devices that haven’t received the newer certificates will continue to start, and standard Windows updates will continue to install. We will continue to install the newer certificates via Windows updates in the coming months.

Summary

This article lists the security issues and quality improvements included in this cumulative security update.

Applies to: Windows 10 ESU

Important Use EKB KB5015684 to update to Windows 10, version 22H2.

This security update includes fixes and quality improvements that are part of the following updates:

The following is a summary of the issues that this update addresses when you install this update. If there are new features, it lists them as well. The bold text within the brackets indicates the item or area of the change we are documenting.

  • [Backup] File History automatic backups to network shares using Server Message Block (SMB) might fail with an incorrect "invalid credentials" error. When this issue occurs, scheduled backups do not copy any files. This update resolves the issue.
  • [Secure Boot] This update includes additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Certificate deployment via Windows updates continues across supported PCs and non-managed business devices in the coming months.

If you installed earlier updates, only the new updates contained in this package will be downloaded and installed on your device.

For more information about security vulnerabilities, please refer to the new Security Update Guide website and the August 2026 Security Updates.

For information about Windows update terminology, see the article about the types of Windows updates and the monthly quality update types. For an overview of Windows 10, version 22H2, see its update history page.

Known issues in this update

We are currently not aware of any issues with this update

Windows 10 servicing stack update (KB5104021) - version 19041.7546

Microsoft now combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). SSUs improves the reliability of the update process and includes fixes to the servicing stack, the component that installs Windows updates.

Note This servicing stack update (SSU) includes enhanced logic to verify whether a device is hosted on Azure, leveraging an updated certificate chain for validation. To ensure that the device can access the required certificate update domains to successfully download and install certificate updates, see Certificate downloads and revocation lists and Azure Certificate Authority details. To learn more about SSUs, see Servicing stack updates.

How to get this update

Before you install this update

Important You must have the latest servicing stack update (SSU) installed. Not installing the latest SSU before applying Windows updates might result in the Windows update not being offered until the latest SSU is installed.

Deployment

If you deploy this update, choose one of the following based on your installation scenario:

  • For offline OS image servicing: If your image does not have the July 25, 2023 (KB5028244) or later LCU, you must install the special standalone October 13, 2023 SSU (KB5031539) before installing this update.
  • For Windows Server Update Services (WSUS) deployment or when installing the standalone package from Microsoft Update Catalog: If your devices do not have the May 11, 2021 (KB5003173) or later LCU, you must install the special standalone August 10, 2021, SSU (KB5005260) before installing this update.

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 devices 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.

Get and install this update

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

Available Next Step
Available This update will be downloaded and installed automatically from Windows Update.

File information

A list of the files that are included in this update are provided in a CSV (Comma delimited) (*.csv) file. The file can be opened in a text editor such as Notepad or in Microsoft Excel.

Note The English (United States) version of this software update might contain files for additional languages.

Download Download the file information for this cumulative update KB5120249.

Download Download the file information for the SSU (KB5104021) - version 19041.7546 update.