Microsoft Windows 11 24H2 Update Version OS Build 26100.9457

KB5129195 for Windows 11, version 24H2 is an out-of-band cumulative update for OS Build 26100.9457. It adds protection for CVE-2026-62721 and fixes Remote Desktop Services, Hyper-V Plan9 folder sharing, and USB Audio Class 1.0 multichannel audio issues. Reference IDs: KB5122880, KB5124007.

• Includes protections for CVE-2026-62721, a Windows User-Mode Power Service (UMPS) elevation of privilege vulnerability.

• Fixes a Remote Desktop Services issue after KB5122880 that could cause RDP connection and sign-in failures, server unresponsiveness, and related tools such as MMC, RDS Licensing Diagnoser, File Explorer, and the Windows Update page to stop responding.
• Fixes a Hyper-V issue where HCS-managed Linux VMs could not access host folders shared through Plan9.
• Fixes an issue where some USB Audio Class 1.0 devices failed in multichannel modes such as 8-channel or 3D audio.
• Includes servicing stack update KB5124007 with quality improvements to the Windows update installation component.

• After the September 8, 2026 Windows security update, some USB Audio Class 1.0 devices may fail to start or produce audio, showing Code 10, no output, unresponsive volume controls, or unavailable sound settings. Microsoft says a resolution is in progress.

• This is a cumulative out-of-band update and includes updates from previous releases.
• Applies to Windows 11, version 24H2 and Windows 11, version 25H2, but the target build here is 26100.9457 for 24H2.

• Windows release health dashboard
  https://learn.microsoft.com/windows/release-health/

Product Information

Vendor: Microsoft

Product: Windows 11

Product type: Software

Application category: Utilities

Platform: Windows

Variant: 24H2

Version: OS Build 26100.9457

Vendor information published: Sep 14, 2026

Original release notes: View on vendor site

Published on updatealert.io: Sep 17, 2026

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