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KB5124008: Overview with user sentiment and feedback

Last Updated October 31, 2026

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Known Issues

Overview

KB5124008 is the September 8, 2026 Patch Tuesday cumulative update for Windows 11 24H2 and 25H2 (OS Builds 26200.9445 and 26100.9445), bundling the September 2026 security fixes with a servicing stack update (KB5124007). It targets all editions of Windows 11 24H2 and 25H2, and Microsoft's own known-issues list for it is long. Community reports point to domain trust failures on Credential Guard/Machine Identity Isolation-enabled machines and to a USB audio regression.

General Purpose

  • Monthly security rollup covering September 2026 Patch Tuesday vulnerabilities, plus a servicing stack update (KB5124007)
  • Adds taskbar position and size options, a smaller Start menu, and Windows Search tweaks
  • Adds Machine Identity Isolation settings that Windows now honors, and updated Secure Boot certificate targeting
  • Fixes Arm64 Teams/Outlook crashes, black desktop backgrounds, mouse cursor settings, and Remote Desktop audio redirection
  • Updates the Morocco time zone for its permanent UTC+00:00 transition

General Sentiment

Reception is strongly negative, with administrators on Reddit and Microsoft Q&A reporting secure-channel failures and lockouts after installation. Some users report the update fixed earlier problems and that it has run without issues on their systems. Forum reports skew toward complaints, but Microsoft has acknowledged the domain trust problem, so the concerns are not isolated.

Known Issues

  • Domain-joined devices with Credential Guard may lose secure channel to Active Directory, causing domain login failures (resolved per Microsoft, via KB5124010 and later)
  • USB Audio Class 1.0 devices may fail to start or produce no sound (partially resolved by out-of-band KB5129195)
  • Hyper-V Linux VMs using Plan9 may lose host folder shares, affecting WSL and similar tools (resolved in KB5129195)
  • Remote Desktop Services may stop responding or cause RDP sign-in failures (resolved in KB5129195)
  • File History may fail to create or update backups (resolved in KB5124010)

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 2026-10-31 02:12 AM

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