September 9, 2025—KB5065430 (OS Build 10240.21128)

Summary

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

Windows 10, version 1507

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

• August 12, 2025—KB5063889 (OS Build 10240.21100)

The following is a summary of the issues that this update addresses. The bold text within the brackets indicates the item or area of the change we are documenting.

• [App compatibility (known issue)] Fixed: Addresses an issue that caused non-admin users to receive unexpected User Account Control (UAC) prompts when MSI installers perform certain custom actions. These actions might include configuration or repair operations in the foreground or background, during the initial installation of an application.

  This issue could prevent non-admin users from running apps that perform MSI repairs, including Office Professional Plus 2010 and multiple applications from Autodesk (including AutoCAD). This fix reduces the scope for requiring UAC prompts for MSI repairs and enables IT admins to disable UAC prompts for specific apps by adding them to an allowlist. For more information, see Unexpected UAC prompts when running MSI repair operations after installing the August 2025 Windows security update.

• [File Server] New! This update enables auditing SMB client compatibility for SMB Server signing as well as SMB Server EPA. This allows customers to assess their environment and identify any potential device or software incompatibility issues before deploying the hardening measures that are already supported by SMB Server. For detailed guidance, see CVE-2025-55234 | Windows SMB Elevation of Privilege Vulnerability.

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 September 2025 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 1507, see its update history page.

Known issues in this update

Microsoft is not currently aware of any issues with this update.

How to get this update

Before you install this update

To install any Windows 10, version 1507 cumulative update released on or after January 14, 2025, you must first install the latest Servicing Stack Update (SSU). If your device or offline image does not have the latest SSU installed, you cannot install this update.

• If you use Windows Update, the latest SSU (KB5065766) will be offered to you automatically. After the latest SSU is installed, you will be able to install this update.

• If you use Windows Update for Business, the latest SSU (KB5065766) will be offered to you automatically. After the latest SSU is installed, you will be able to install this update.

• If you use the Update Catalog, you must download and install the latest SSU (KB5065766). After the latest SSU is installed, you will be able to install this update.

• If you are a Windows Server Update Services (WSUS) administrator, you must approve SSU KB5065766 and this update KB5065430.

For general information about SSUs, see Servicing stack updates and Servicing Stack Updates (SSU): Frequently Asked Questions.

Install this update

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

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.

Download the file information for this cumulative update KB5065430 now.