Microsoft Windows 11 26H1 Update Version OS Build 28000.2954

KB5124012 for Windows 11 version 26H1 updates OS Build 28000.2954 with the latest security fixes and non-security improvements from KB5120996. It also improves Secure Boot targeting, fixes Teams and Outlook crashes on Arm64, and addresses Remote Desktop audio redirection issues. Reference IDs: KB5125104.

• Provides security improvements and resolves vulnerabilities referenced by the Security Update Guide.
• Improves Secure Boot certificate deployment coverage by adding high-confidence device targeting data.

• Fixes Microsoft Teams and Microsoft Outlook unexpectedly closing on Arm64-based PCs.
• Fixes Remote Desktop audio redirection issues that could prevent remote audio from playing locally in some configurations.
• Improves OMA-DM client diagnostic logging by adding certificate chain information for server connections.
• Adjusts Morocco Standard Time for the transition to permanent UTC+00:00 on Sep 20, 2026.

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

• If previous updates are already installed, only the new updates in this package will be downloaded and installed.
• Includes servicing stack update KB5125104 (Build 28000.2950) to improve the reliability of the Windows update installation process.
• AI components are updated to version 1.2608.951.0 for Image Search, Content Extraction, Semantic Analysis, and Settings Model.

• Servicing stack update guidance
  https://learn.microsoft.com/windows/deployment/update/servicing-stack-updates#simplifying-on-premises-deployment-of-servicing-stack-updates

Product Information

Vendor: Microsoft

Product: Windows 11

Product type: Software

Application category: Utilities

Platform: Windows

Variant: 26H1

Version: OS Build 28000.2954

Vendor release date: Sep 8, 2026

Original release notes: View on vendor site

Published on updatealert.io: Sep 9, 2026

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