Microsoft Windows 11 25H2 Update Version OS Builds 26200.9457 and 26100.9457

KB5129195 is an out-of-band cumulative update for Windows 11 version 25H2. It adds protection for CVE-2026-62721 and fixes Remote Desktop Services, Hyper-V Plan9 folder sharing, and USB multichannel audio issues. Reference IDs: KB5124007.

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

• Fixes Remote Desktop Services instability after KB5122880 that could cause RDP sign-in failures, unresponsive servers, and related tools to stop responding.
• Fixes Hyper-V issues where HCS-managed Linux VMs could not access host folders shared through Plan9.
• Fixes USB Audio Class 1.0 devices failing in multichannel audio modes such as 8-channel or 3D audio.

• After the September 8, 2026 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.

• This is a cumulative out-of-band update for Windows 11 version 25H2 and 24H2.
• Includes Windows 11 servicing stack update KB5124007 (build 22621.9441).
• Microsoft says it is working on a resolution for the USB Audio Class 1.0 known issue.

• KB5129195 release notes
  https://support.microsoft.com/help/5129195

Product Information

Vendor: Microsoft

Product: Windows 11

Product type: Software

Application category: Utilities

Platform: Windows

Variant: 25H2

Version: OS Builds 26200.9457 and 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.