Windows 11 KB5124012, KB5124008 & KB5122880 September 2026 Patch Tuesday Updates Released

Microsoft has released the September 2026 Patch Tuesday updates, KB5124012, KB5124008, and KB5122880, for Windows 11 version 26H1, 25H2/24H2, and 23H2, respectively. The latest monthly security update focuses on security improvements, while also addressing several annoying issues stemmed from multiple past updates. For example, the latest Patch Tuesday updates fix Teams and Outlook launch issues on Arm64 PCs on Windows 11 26H1, 24H2, and 25H2.

Similarly, the KB5124008 fixes the mouse and desktop personalization issues. Besides those, Microsoft has also taken care of Date & Time adjustments, Remote Desktop Audio Redirection issues, and improves diagnostic logging for the OMA-DM client.

That’s not all; the September 2026 Patch Tuesday updates, KB5124012, KB5124008, and KB5122880, also expands device targeting for Microsoft’s Secure Boot certificate rollout. Microsoft says newer certificates will continue arriving through Windows Update over coming months. You can find the changelog for each patch below:

KB5124008 for Windows 11 24H2 and 25H2 (Build 26100.944 and 26200.9445)

• [Security updates] This update provides security improvements. For more information about the security vulnerabilities resolved by this update.
• [Secure Boot] This update includes additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Certificate deployment via Windows updates continues across supported PCs and non-managed business devices in the coming months.
• [Mouse] Fixed: This update addresses an issue that prevented customized mouse cursor settings, including pointer style and color, from displaying correctly. Selected cursor options and colors now work as expected.
• [Personalization] Fixed: This update addresses an issue where desktop background and other personalization settings might not load correctly, causing the desktop background to appear black.
• [Teams and Outlook on Arm64 PCs] Fixed: This update addresses an issue that could cause Microsoft Teams and Microsoft Outlook to unexpectedly close on Arm64-based PCs.
• [Date and Time] This update adjusts Morocco Standard Time to reflect Morocco’s transition to permanent UTC+00:00 effective September 20, 2026. This change ensures that the correct local time is displayed after the transition.
• [Remote Desktop Audio Redirection] This update addresses an issue affecting Remote Desktop audio redirection that could prevent audio from a remote session from playing on the local device in certain configurations.
• [OMA-DM Client Logging] This update improves diagnostic logging for the OMA-DM client, providing additional information to help troubleshoot device management server connection issues.

KB5124012 for Windows 11 26H1 (Build 28000.2954)

• [Security updates] This update provides security improvements. For more information about the security vulnerabilities resolved by this update.
• [Secure Boot] This update includes additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Certificate deployment via Windows updates continues across supported PCs and non-managed business devices in the coming months.
• [Teams and Outlook on Arm64 PCs] Fixed: This update addresses an issue that could cause Microsoft Teams and Microsoft Outlook to unexpectedly close on Arm64-based PCs.
• [Date and Time] This update adjusts Morocco Standard Time to reflect Morocco’s transition to permanent UTC+00:00 effective September 20, 2026. This change ensures that the correct local time is displayed after the transition.
• [Remote Desktop Audio Redirection] This update addresses an issue affecting Remote Desktop audio redirection that could prevent audio from a remote session from playing on the local device in certain configurations.
• [OMA-DM Client Logging] This update improves diagnostic logging for the OMA-DM client by adding certificate chain information for server connections, helping administrators troubleshoot device management connectivity issues.

KB5122880 for Windows 11 23H2 (Build 22621.7582)

• [Security updates] This update provides security improvements. For more information about the security vulnerabilities resolved by this update.
• [Secure Boot] This update includes additional high confidence device targeting data, increasing coverage of devices eligible to automatically receive new Secure Boot certificates. Certificate deployment via Windows updates continues across supported PCs and non-managed business devices in the coming months.
• [Date and Time] This update adjusts Morocco Standard Time to reflect Morocco’s transition to permanent UTC+00:00 effective September 20, 2026. This change ensures that the correct local time is displayed after the transition.
• [Cellular] Updating COSA profiles for Telavox and Swisscom.
• [OMA DM] This update improves the logging features of the Omadmclient component. More debug information is now saved when connecting to a server.
• [Remote Desktop] This update addresses an issue that affects Remote Desktop audio redirection. Audio from the remote session might not play on the local computer in certain configurations.

Do note that all of the updates listed above should be installed automatically via Windows Update on your PC.