What's new in KB5094126 (Windows 11 build 26200.8655)
- Windows 11 version 25H2 (Build 26200.8655)
- Windows 11 version 24H2 (Build 26100.8655)
Maya Reyes3 min readQuick answer
KB5094126 is a mandatory cumulative security update released on June 9, 2026, for Windows 11 version 25H2 (Build 26200.8655) and Windows 11 version 24H2 (Build 26100.8655). It includes critical security patches, core operating system maintenance, and servicing stack updates. Windows Update will download and install this Patch Tuesday update automatically.
Microsoft released KB5094126 on June 9, 2026, as a mandatory cumulative update for Windows 11. This update arrives as part of Microsoft's regular Patch Tuesday schedule, delivering security hardening, reliability fixes, and system maintenance across supported devices. The update applies specifically to two versions of the operating system: Windows 11 version 25H2, which advances to OS Build 26200.8655, and Windows 11 version 24H2, which advances to OS Build 26100.8655.
Because KB5094126 is a mandatory security release rather than an optional preview build, Windows Update will automatically download and install it in the background. Understanding what this update changes helps you verify that your PC is up to date and functioning properly after the installation finishes.
Highlights
- Windows 11 version 25H2 build bump: Advances systems running Windows 11 version 25H2 to OS Build 26200.8655.
- Windows 11 version 24H2 build bump: Advances systems running Windows 11 version 24H2 to OS Build 26100.8655.
- Monthly security maintenance: Includes the complete set of security patches released on June 9, 2026, targeting vulnerabilities in underlying operating system components.
- Servicing stack updates: Delivers background updates to the servicing stack, which handles system updates to ensure future installations proceed without errors.
- Consolidated update package: Incorporates earlier non-security quality improvements and bug fixes from previous preview releases, including KB5089573, into a single update.
Because Windows 11 version 25H2 and Windows 11 version 24H2 share a common underlying core, Microsoft builds and deploys cumulative updates for both branches simultaneously. When KB5094126 installs, it updates shared system files, patches vulnerabilities across network and kernel services, and updates internal build tracking. This shared update model ensures consistent security protection and performance optimizations across both version 24H2 and version 25H2 installations.
Known issues
Microsoft reports no known issues for this update.
Should you install it?
Yes, you should install KB5094126 promptly. Because this is a Patch Tuesday security update, it addresses critical security vulnerabilities that could leave your device exposed if left unpatched. Skipping or delaying security updates increases your exposure to potential software threats and system vulnerabilities.
Most users do not need to take any special action, as Windows Update handles the installation automatically. If you are in the middle of important work, you can set your active hours in Settings so your PC does not restart unexpectedly. Given that Microsoft reports no known issues with KB5094126, installing it as soon as it becomes available is the recommended choice for maintaining system stability and security.
How to get it
Illustration: the Troubleshoot > Other troubleshooters page under Settings > System
You can obtain KB5094126 through standard Windows Update or download it manually from the Microsoft Update Catalog.
To install the update using Windows Update:
- Open the Start menu and select Settings, or press Windows Key + I on your keyboard.
- In the left navigation bar, click on Windows Update.
- Click the Check for updates button on the right side of the screen.
- Wait while Windows Update scans for available updates. KB5094126 should appear and begin downloading automatically.
- Once the download and installation phases complete, click Restart now to finish applying the update.
If your system encounters errors during the automatic update process, you can download the standalone package directly:
- Open your browser and navigate to the official Microsoft Update Catalog website.
- In the search box at the top right, enter KB5094126 and press Enter.
- Review the list of search results to find the build matching your operating system version (Windows 11 version 25H2 Build 26200.8655 or Windows 11 version 24H2 Build 26100.8655) and system architecture (x64 or ARM64).
- Click the Download button next to the matching entry.
- In the pop-up window, click the link to download the standalone .msu file.
- Once downloaded, double-click the .msu file to run the installer, then follow the prompts to complete the installation and restart your system.
If the update fails to install or gets stuck during the download phase, run the Windows Update troubleshooter in Settings under System > Troubleshoot > Other trouble-shooters, or clear the Windows Update temporary files before attempting the installation again.
Sources
Frequently asked questions
What OS builds does KB5094126 bring to Windows 11?
KB5094126 advances Windows 11 version 25H2 to OS Build 26200.8655 and Windows 11 version 24H2 to OS Build 26100.8655.
Is KB5094126 an optional update?
No, KB5094126 is a mandatory Patch Tuesday security update released on June 9, 2026. Windows Update installs it automatically unless update pauses are enabled.
What should I do if KB5094126 fails to install?
If KB5094126 encounters an installation error, run the built-in Windows Update troubleshooter in Settings or download the standalone .msu package directly from the Microsoft Update Catalog.
Does KB5094126 apply to Windows 11 version 23H2?
No, KB5094126 applies to Windows 11 version 25H2 and version 24H2. Windows 11 version 23H2 received a separate update (KB5093998) on June 9, 2026.
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Covers Windows 11 update releases and the problems that follow them. Tracks Microsoft's release-health notes daily and flags known issues the same day they appear.
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