September 22, 2025—KB5068221 (OS Build 26100.6588) Out-of-band
Applies To
Release Date:
9/22/2025
Version:
OS Build 26100.6588
Windows Secure Boot certificate expirationImportant: Secure Boot certificates used by most Windows devices are set to expire starting in June 2026. This might affect the ability of certain personal and business devices to boot securely if not updated in time. To avoid disruption, we recommend reviewing the guidance and taking action to update certificates in advance. For details and preparation steps, see Windows Secure Boot certificate expiration and CA updates.
To learn about Windows update terminology, see the pages on types of Windows updates and monthly quality update types. For an overview, see the update history page for Windows 11, version24H2.  Â
Follow @WindowsUpdate to find out when new content is published to the Windows Release Health Dashboard.Â
 Improvements
This Out-of-band (OOB) update includes quality improvements. This update is cumulative and includes security fixes and improvements from the September 9, 2025, security update (KB5065426), in addition to the following:Â
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[Virtualization and platform compatibility]Â Fixed:Â This update addresses an issue that affects Microsoft Office applications running in Microsoft Application Virtualization (App-V) environments. The failure occurred due to a double handle closure in the AppVEntSubsystems32 or AppVEntSubsystems64Â system component.
AI Components
This release updates the following AI components:
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AI Component |
Version |
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Image Search |
1.2508.906.0 |
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Content Extraction |
1.2508.906.0 |
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Semantic Analysis |
1.2508.906.0 |
|
Settings Model |
1.2508.906.0 |
Windows 11 servicing stack update (KB5064531)- 26100.5074
This update makes quality improvements to the servicing stack, which is the component that installs Windows updates. Servicing stack updates (SSU) ensure that you have a robust and reliable servicing stack so that your devices can receive and install Microsoft updates. To learn more about SSUs, see Simplifying on-premises deployment of servicing stack updates.
Known issues in this update
Symptoms
After installing this Windows update released on or after September 9, 2025, you might fail to connect to shared files and folders using the Server Message Block (SMB) v1 protocol on NetBIOS over TCP/IP (NetBT). This issue can occur if either the SMB client or the SMB server has the September 2025 security update installed.
Note: The SMBv1 protocol is deprecated and no longer installed by default in modern versions of Windows and Windows Server. Deployments that use newer versions of the protocol, SMBv2 or SMBv3, are not affected by this problem.
Workaround
You can work around this issue by allowing network traffic on TCP port 445. By doing so, the Windows SMB connection will automatically switch to using TCP instead of NetBT, allowing the connection to resume successfully.
Next steps: We are working on a resolution in a future Windows update and will provide more information when it is available.
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 and Servicing Stack Updates (SSU): Frequently Asked Questions.Â
Install this update
To install this update, use one of the following Windows and Microsoft release channels.
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Before you install this update To get the standalone package(s) for this update, go to the Microsoft Update Catalog website. This KB contains one or more MSU files that require installation in a specific order. Install this update Method 1: Install all MSU files together Download all MSU files for KB5068221 from Microsoft Update Catalog and place them in the same folder (for example, C:/Packages). Use Deployment Image Servicing and Management (DISM.exe) to install the target update. DISM will use the folder specified in PackagePath to discover and install one or more prerequisite MSU files as needed. Updating Windows PC To apply this update to a running Windows PC, run the following command from an elevated Command Prompt:
Or, run the following command from an elevated Windows PowerShell prompt:
Updating Windows Installation media To apply this update to Windows Installation media, see Update Windows installation media with Dynamic Update. Note: When downloading other Dynamic Update packages, ensure they match the same month as this KB. If the SafeOS Dynamic Update or Setup Dynamic Update is not available for the same month as this KB, use the most recently published version of each. To add this update to a mounted image, run the following command from an elevated Command Prompt:
Or, run the following command from an elevated Windows PowerShell prompt:
​​​​​​​Method 2: Install each MSU file individually in order Download and install each MSU file individually using DISM or Windows Update Standalone Installer in the following order:
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1 This latest cumulative update includes updates for AI components. Even though the AI component updates are included in the update, the AI components are only applicable to Windows Copilot+ PCs and will not install on Windows PC or Windows Server.
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If you want to remove the LCU
To remove the LCU after installing the combined SSU and LCU package, use the DISM/Remove-Package command line option with the LCU package name as the argument. You can find the package name by using this command: DISM /online /get-packages.
Running Windows Update Standalone Installer (wusa.exe) with the /uninstall switch on the combined package will not work because the combined package contains the SSU. You cannot remove the SSU from the system after installation.
File information
For a list of the files provided in this update, download the file information for cumulative update 5068221.Â
For a list of the files provided in the servicing stack update, download the file information for the SSU KB5064531 - version 26100.5074. Â
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