KB5124012

Microsoft has released the cumulative security update KB5124012 (Build 28000.2954) for Windows 11 version 26H1 as part of Patch Tuesday for September 2026. The update contains a number of improvements and fixes aimed at increasing the stability, security, and usability of the operating system. Special attention is paid to audio functions, compatibility with ARM64 devices, and the correct operation of system components.

• Voice Isolation. A feature has been added to suppress background noise during audio recording, which improves the quality of voice input and recording in noisy environments.
• Automatic volume leveling. Improvements have been made to ensure automatic leveling of sound volume for more comfortable perception.
• New sound controls. Additional sound controls have appeared in the Settings app, expanding audio configuration options.
• Stability of window transitions. Fixed issues where transitions between application windows could work inconsistently. Switching has now become smoother and more reliable.
• Mail and calendar synchronization. Resolved issues affecting data synchronization for mail and calendar.
• Faster File Explorer and clipboard. Improved performance of File Explorer and the clipboard, speeding up everyday file and text operations.
• Support for Myanmar Text and Mongolian Baiti fonts. Added support for these fonts, improving text rendering in the corresponding languages.
• Updated time zones. Updated time zone settings for Morocco, Israel, and Greenland. In particular, Morocco will switch to permanent UTC+00:00 time starting September 20, 2026.
• DHCP fixes. Resolved issues related to DHCP protocol operation.
• IPPS printing fixes. Resolved issues affecting printing via the IPPS protocol.
• Azure Virtual Desktop compatibility. Fixes have been made to improve compatibility with Azure Virtual Desktop.
• Secure Boot. Microsoft has expanded the list of devices that can automatically receive new Secure Boot certificates. Their distribution through the Windows Update service will continue in the coming months on supported consumer and unmanaged corporate PCs.
• Microsoft Teams and Outlook (ARM64). Fixed an issue where Microsoft Teams and Microsoft Outlook could unexpectedly terminate on computers with ARM64 architecture.
• Remote Desktop. Fixed an audio redirection issue where, in some configurations, sound from a remote session was not played on the local device.
• OMA-DM client. Diagnostic logging has been improved. Information about the certificate chain of server connections has been added, which will help administrators identify problems connecting devices to the management system.

To install update KB5124012, open Settings, go to Windows Update, and click Check for updates. The system will find and offer to install the cumulative update. A computer restart will be required to complete the installation.

The update can also be downloaded manually from the Microsoft Update Catalog if automatic installation is unavailable for any reason. Additionally, it is worth noting that the update includes all previously released fixes for Windows 11 version 26H1, so separate previous patches do not need to be installed after it.

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