KB5129195: Overview with user sentiment and feedback

Overview

KB5129195 is an out-of-band (OOB) emergency security update released September 14, 2026, for Windows 11 versions 25H2 and 24H2 (builds 26200.9457 and 26100.9457). It addresses critical issues introduced by the September 8 Patch Tuesday update (KB5124008), including Remote Desktop Services (RDS) instability, USB audio device failures, and Hyper-V Plan9 folder-sharing problems. The update also includes an additional security fix for CVE-2026-62721 (Windows User-Mode Power Service elevation of privilege).

General Purpose

• Remote Desktop Services fix: Resolves RDS instability, connection failures, and unresponsive MMC/File Explorer after KB5124008
• USB Audio Class 1.0 support: Fixes multichannel audio (8-channel, 3D modes) on some USB devices; standard stereo audio issues remain unresolved
• Hyper-V Plan9 folder sharing: Restores access to Windows host folders shared with Linux VMs using Plan9
• Claude Cowork and WSL apps: Fixes storage access issues for HCS-managed virtual machines
• CVE-2026-62721 security patch: Additional protections for Windows User-Mode Power Service elevation of privilege vulnerability
• Desktop loading issues (partial): Known Issue Rollback (KIR) available via Group Policy for black screen/FSLogix-related problems

General Sentiment

Community reception is mixed. The update successfully fixes several critical issues (RDS, Hyper-V, some audio), and many users report successful installations. However, reports indicate installation failures (error codes 0x800f081f, 0x800705b9), persistent audio issues on USB devices, unresolved Explorer.exe crashes, File History breakage, and AMD GPU errors. Some sysadmins report domain trust issues and deployment hesitation. The emergency nature of the release suggests the September 2026 update cycle introduced widespread regressions.

Known Issues

• Devices may experience black screen or desktop loading issues after sign-in (workaround: manual explorer.exe launch or KIR via Group Policy)
• Domain-joined machines with Credential Guard may lose secure channel with Active Directory (resolved in KB5124010)
• USB Audio Class 1.0 devices with Code 10 errors or no audio output (partial fix; some audio symptoms remain unresolved)
• File History unable to detect or backup to external drives
• Explorer.exe crashes on sign-in (primarily affects AVD/FSLogix environments)
• AMD GPU errors (black screens, driver timeouts, display failures) not addressed by this update

Disclaimer: We take measures to ensure that AI-generated content is of the highest possible quality, but we cannot guarantee its accuracy and recommend that users do their own independent research. Generated on 2026-10-13 06:49 AM

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