Microsoft Windows 11 25H2 Update Version OS Builds 26200.9550 and 26100.9550

KB5124010 for Windows 11 version 25H2 and 24H2 delivers quality improvements, new features, and fixes. It also includes SSU KB5124009 and notes known issues affecting domain-joined devices and USB Audio Class 1.0 devices. Reference IDs: KB5124008.

• Security hardening for Windows Secure Boot certificate updates on affected devices.
• Known issue: domain-joined devices may lose secure trust relationship after KB5124008 or later when Machine Identity Isolation enforcement is enabled in unsupported environments.

• Fixes a File Explorer address bar issue that could clear contents when entering edit mode.
• Improves File Explorer preview pane behavior for web-downloaded files and cloud file thumbnails in Details pane.
• Improves Bluetooth reliability, including audio stability, connection state accuracy, Settings stability, and a crash during Bluetooth audio streaming.
• Fixes Settings issues for Bluetooth and Devices, Printers and Scanners, installed app version display, time picker format, and camera setting persistence.
• Fixes a camera issue where the built-in camera might stop working in Camera app and other apps.
• Fixes File History backup and restore failures to external drives or network locations.
• Fixes Sysmon issues with executable header validation, file system filter driver stop errors, and incorrect Event ID 25 alerts for smss.exe.
• Improves desktop background reliability, slideshow transitions, preview quality, and multi-desktop slideshow wallpaper behavior.
• Improves power and battery behavior when a plugged-in laptop incorrectly switches from AC to battery power.

• Adds a Tips widget for Widgets board and lock screen.
• Adds Emoji 17.0 support and refreshes several existing emoji designs.
• Adds Open apps maximized accessibility setting.
• Modernizes the Magnifier taskbar with updated icons and spacing.
• Adds support for DIB image files as desktop backgrounds.
• Adds support for slideshow wallpapers across multiple desktops.
• Adds a Copilot key remapping setting for Right Ctrl or Context Menu.
• Adds Camera roll backup setup in Settings with OneDrive and QR code flow.
• Adds Garay and Beria Erfe script support to the Ebrima font and refines Adlam glyphs.
• Adds a recovery remote management plug-in for WinRE management by MDM providers.
• Adds additional precision touchpad gestures for single-finger scrolling and automatic scrolling.

• Domain-joined devices might lose their secure trust relationship with the domain when Machine Identity Isolation enforcement is enabled in unsupported environments.
• USB Audio Class 1.0 devices may fail to start or produce audio, showing Code 10 or no output after the September 8, 2026 security update.

• Final preview update for Windows 11 version 24H2; customers needing preview releases should move to a newer Windows 11 version.
• PC-to-PC Migration is no longer available; use Windows Backup instead.
• For deployment of dynamic updates to existing Windows images, include boot.stl in installation media to avoid startup failures and error 0xc0430001.
• If Machine Identity Isolation was enabled by policy or registry, disable it using the same management method and restart the device before repairing the secure channel.
• The update includes SSU KB5124009 (Build 26100.9539).

Product Information

Vendor: Microsoft

Product: Windows 11

Product type: Software

Application category: Utilities

Platform: Windows

Variant: 25H2

Version: OS Builds 26200.9550 and 26100.9550

Vendor information published: Sep 22, 2026

Original release notes: View on vendor site

Published on updatealert.io: Sep 24, 2026

Description: Client operating system for modern desktop and enterprise environments.