KB5124012: Overview with user sentiment and feedback
Last Updated October 31, 2026
Probability of successful installation and continued operation of the machine
Overview
KB5124012 is the September 8, 2026 cumulative update for Windows 11 version 26H1 (OS Build 28000.2954), bundling the August 2026 preview changes with new security fixes. It also ships a servicing stack update (KB5125104). Sources list it as applying to all editions of Windows 11 26H1; it is delivered via Windows Update, WUfB, WSUS, and the Update Catalog.
General Purpose
- Security fixes plus non-security updates carried over from the August 2026 preview (KB5120996)
- Expands Secure Boot certificate device targeting for automatic certificate deployment
- Fixes Teams and Outlook unexpectedly closing on Arm64 PCs
- Updates Morocco Standard Time for its permanent UTC+00:00 switch on September 20, 2026
- Fixes Remote Desktop audio redirection failures in certain configurations and adds OMA-DM certificate chain logging
- Includes Machine Identity Isolation settings that can break domain trust on non-2025 DFL domains (see known issues)
General Sentiment
Microsoft's own release notes list several serious problems, and the source pages provide no substantive community discussion to offset them. Several of the listed issues have since been resolved by later updates, which points to real breakage in this release. Reception is therefore cautious, and the update should be deployed only after the later fixes are in place.
Known Issues
- Domain-joined devices with Credential Guard may lose secure channel trust with AD (resolved by KB5124010 per Microsoft; marked resolved October 7, 2026)
- Devices may show black screen or desktop load failures after sign-in (linked to August preview KB5120996 and later updates; resolved in Windows updates from October 13, 2026 such as KB5127646)
- USB Audio Class 1.0 devices may fail to start or produce no sound (partially fixed by OOB KB5129194; other symptoms still under investigation)
- Hyper-V Linux VMs using Plan9 may lose host folder shares, affecting WSL and similar apps (resolved in updates from September 14, 2026 such as KB5129194)
- Remote Desktop Services may hang or stop responding, and Windows Update may stall (resolved in updates from September 14, 2026 such as KB5129194; does not affect Windows 365 or AVD)
- File History may fail to create or update backups (resolved in updates from September 22, 2026 such as KB5124006)
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 02:06 PM
