Microsoft released cumulative update KB5124008 for Windows 11 version 26H2 (2026 Update) as part of Patch Tuesday for September 2026. The update brings changes to the Start menu and taskbar, improved integration of Microsoft Store apps along with support for the WinUI 3 interface, support for the ML-KEM algorithm in TLS connection encryption, fixes for network connectivity and VPN issues, as well as increased stability of Settings and optimization of the system kernel. In addition, Microsoft warned about the upcoming end of support for the WMIC utility.
- Secure Boot. Microsoft added additional data to more accurately identify devices that can automatically receive new Secure Boot certificates. In the coming months, Microsoft will continue to distribute certificates through the Windows Update service to supported computers, including user devices and unmanaged corporate PCs.
- Mouse. Fixed an issue where user mouse cursor settings, including pointer style and color, were displayed incorrectly. The selected cursor options and colors should now apply as intended.
- Personalization. Fixed an issue where the desktop background and other personalization settings could load incorrectly. In particular, due to the error, a black background could be displayed instead of the selected wallpaper.
- Microsoft Teams and Outlook for ARM64. Fixed an issue where Microsoft Teams and Microsoft Outlook could unexpectedly close on computers with ARM64 processors.
- Date and Time. Changed Morocco time zone settings due to the country's transition to permanent UTC+00:00 time starting September 20, 2026. The change should ensure correct display of local time after the transition.
- Remote Desktop. Fixed an issue with audio redirection through Remote Desktop. In some configurations, it caused sound from the remote session not to play on the local device.
- OMA-DM Client. Improved diagnostic logging for the OMA-DM client. Additional information has been added to the logs, which should make it easier to find the causes of problems when connecting a device to a management server.
You can install the update through Windows Update: open Settings, go to the Windows Update section, and click Check for updates. Cumulative update 5124008 for PCs is installed automatically through Windows Update. The build after installing the update is 26300.9445.
| Feature / Change | Performance Increase / Decrease | Optimization | PC Speed Impact | Gaming Optimization |
|---|---|---|---|---|
| Secure Boot certificate identification data | ⚪ No direct impact (background process) | 🟢 Improved update targeting accuracy | ⚪ No measurable change | ⚪ No impact |
| Mouse cursor settings fix | ⚪ No impact | 🟢 Settings now apply correctly (UI fix) | ⚪ No change | 🟡 Minor (accurate cursor rendering in games) |
| Personalization / desktop background fix | 🟡 Slight improvement (no black screen redraw) | 🟢 Correct loading of user preferences | 🟡 Marginal (less UI error recovery) | ⚪ No direct impact |
| Microsoft Teams and Outlook ARM64 crash fix | 🟢 High (prevents unexpected app termination) | 🟢 Stability optimization for ARM64 | 🟢 Noticeable on ARM64 devices | ⚪ Not applicable (productivity apps) |
| Morocco time zone change (UTC+00:00 permanent) | ⚪ No impact | 🟢 Correct local time after transition | ⚪ No change | ⚪ No impact |
| Remote Desktop audio redirection fix | ⚪ No impact | 🟢 Audio now plays locally as intended | ⚪ No change | 🟡 Minor (remote play scenarios) |
| OMA-DM Client diagnostic logging improvement | ⚪ No user-facing impact | 🟢 Better troubleshooting for IT admins | ⚪ No change | ⚪ No impact |
Official announcement on the Microsoft website.
The last 10 Windows updates:
| Update | Build | Version | Windows | Channel | Date |
|---|---|---|---|---|---|
| KB5126657 | 19045.7807 | 22H2 (ESU) | Windows 10 | Stable | 2026-10-13 |
| KB5126653 | 22631.7652 | 23H2 | Windows 11 | Stable | 2026-10-13 |
| KB5127646 | 28000.3231 | 26H1 | Windows 11 | Stable | 2026-10-13 |
| KB5127648 | 26300.9711 | 26H2 | Windows 11 | Stable | 2026-10-13 |
| KB5127757 | 28120.3181 | 26H1 | Windows 11 | Experimental | 2026-10-07 |
| KB5127758 | 26220.9606 | 25H2 | Windows 11 | Beta | 2026-10-07 |
| KB5127754 | 28020.3172 | 26H1 | Windows 11 | Beta | 2026-10-07 |
| KB5127753 | 26340.9616 | 26H2 | Windows 11 | Experimental | 2026-10-07 |
| KB5124192 | 28120.3151 | 26H1 | Windows 11 | Experimental | 2026-10-02 |
| KB5124196 | 28020.3142 | 26H1 | Windows 11 | Beta | 2026-10-02 |