UPDATE 8/27:
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This cumulative update for Windows 11, version 26H1 (KB5121000) includes the latest security fixes and improvements, along with non-security updates from last month's optional preview release. Visit the Windows release health dashboard for the latest status on this release.
Change log
This update addresses security vulnerabilities documented in the following guide:
The following summary outlines key quality improvements addressed by this update. The bold text within the brackets indicates the item or area of the change.
This release updates the following AI components to version 1.2605.856.0: Image Search, Content Extraction, Semantic Analysis, and Settings Model.
To learn more, see Release information for AI components.
Servicing stack update
Includes KB5121292 (Build 28000.2602), which improves the reliability of the Windows update installation process. To learn more about SSUs, see Simplifying on-premises deployment of servicing stack updates.
Microsoft combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). For general information about SSUs, see Servicing stack updates.
Note
The boot.stl file is used during Secure Boot validation and must match the Windows version and architecture of the image you are updating.
To ensure the boot.stl file is included as part of the installation media, do one of the following:
For a list of the files provided in the servicing stack update, download the file information for the SSU (KB5101747) - version 28000.2602.
support.microsoft.com
Check Windows Updates
UUP Dump:
64-bit ISO download:
ARM64 ISO download:
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KB5120996 Windows 11 Cumulative Update Preview build 28000.2804 (26H1) - Aug. 27
Microsoft Support: Source: Check Windows Updates UUP Dump: 64-bit ISO download: https://uupdump.net/selectlang.php?id=8f595bc2-11e8-4b7d-91e0-c457277db89e ARM64 ISO download: https://uupdump.net/selectlang.php?id=deee09e7-795b-4ac6-ad80-a8680e97908d...
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Microsoft Support:
This cumulative update for Windows 11, version 26H1 (KB5121000) includes the latest security fixes and improvements, along with non-security updates from last month's optional preview release. Visit the Windows release health dashboard for the latest status on this release.
Announcements and messages
This section provides key notifications related to this release, including announcements, change logs, and end-of-support notices.Change log
Change date | Change description |
|---|---|
| September 3, 2026 | Known issue added, "Microsoft Teams and Outlook might fail to launch on ARM-based devices." |
| August 17, 2026 | Update added, "[Sharing] This update removes the Drop Tray experience (previously named Drag Tray) for devices where it was available. It also removes the associated setting under Settings > System > Multitasking. We are continuing to evaluate the experience and explore future enhancements." |
Improvements
This update includes new features and quality improvements that were part of the following update:This update addresses security vulnerabilities documented in the following guide:
The following summary outlines key quality improvements addressed by this update. The bold text within the brackets indicates the item or area of the change.
- [Device] This update improves TPM maintenance reporting by ensuring that EK certificate status is reported accurately.
- [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.
- [Sharing] This update removes the Drop Tray experience (previously named Drag Tray) for devices where it was available. It also removes the associated setting under Settings > System > Multitasking. We are continuing to evaluate the experience and explore future enhancements.
Enable or Disable Drop Tray in Windows 11
This tutorial will show you how to enable or disable the Drag/Drop Tray feature for your account in Windows 11. Starting with Windows 11 build 26100.4202 (24H2) and build 22631.5413 (23H2), sharing files in Windows is getting a lot easier and quicker with the Drag Tray feature. When you start...
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Components updates
AI componentsThis release updates the following AI components to version 1.2605.856.0: Image Search, Content Extraction, Semantic Analysis, and Settings Model.
To learn more, see Release information for AI components.
Servicing stack update
Includes KB5121292 (Build 28000.2602), which improves the reliability of the Windows update installation process. To learn more about SSUs, see Simplifying on-premises deployment of servicing stack updates.
Known issues in this update
Symptoms
After installing Windows security updates released on or after August 11, 2026, (KB5121000), Microsoft Teams and the new Outlook for Windows might fail to launch or might close unexpectedly on ARM-based devices, such as Surface Pro 11 and Surface Laptop 7. Classic Outlook, Word, Excel, and other applications are not known to be affected. This issue is most likely to occur on new or freshly imaged PCs that have not yet installed any Microsoft Store updates.
Workaround
To work around this issue:
We are working on releasing a resolution for this issue in a future Windows update. We will provide an update when more information is available.
After installing Windows security updates released on or after August 11, 2026, (KB5121000), Microsoft Teams and the new Outlook for Windows might fail to launch or might close unexpectedly on ARM-based devices, such as Surface Pro 11 and Surface Laptop 7. Classic Outlook, Word, Excel, and other applications are not known to be affected. This issue is most likely to occur on new or freshly imaged PCs that have not yet installed any Microsoft Store updates.
Workaround
To work around this issue:
- Open Microsoft Store.
- Select Downloads > Check for updates.
- Install the latest update for the Auto Super Resolution Package (version 1.0.19.0 or later).
We are working on releasing a resolution for this issue in a future Windows update. We will provide an update when more information is available.
How to get this update
Before you install this updateMicrosoft combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). For general information about SSUs, see Servicing stack updates.
Deployment
If you deploy dynamic updates such as this update to an existing Windows image, ensure the boot.stl file is included as part of the installation media. Failure to include the file might prevent devices from successfully starting from the installation media and can result in error code 0xc0430001.Note
The boot.stl file is used during Secure Boot validation and must match the Windows version and architecture of the image you are updating.
To ensure the boot.stl file is included as part of the installation media, do one of the following:
- Use the Update WinPE script to update an existing Windows image. (Recommended)
- Manually copy the boot.stl file from the device Windows\Boot\EFI folder to the corresponding folder on your installation media before deploying the update.
Install this update
To install this update, use one of the following Windows and Microsoft release channels.| Available | Next Step |
|---|---|
 | This update downloads and installs automatically from Windows Update and Microsoft Update. |
| To install this release from the Microsoft Update Catalog, follow these instructions: |
File information
For a list of the files provided in this update, download the file information for cumulative update KB5121000.For a list of the files provided in the servicing stack update, download the file information for the SSU (KB5101747) - version 28000.2602.
Source:
August 11, 2026—KB5121000 (OS Build 28000.2704) | Microsoft Support
August 11, 2026—KB5121000 (OS Build 28000.2704)
support.microsoft.com
Check Windows Updates
UUP Dump:
64-bit ISO download:
Select language for Windows 11, version 26H1 (28000.2704) amd64
Select language for Windows 11, version 26H1 (28000.2704) amd64 on UUP dump. UUP dump lets you download Unified Update Platform files, like Windows Insider updates, directly from Windows Update.
uupdump.net
ARM64 ISO download:
Select language for Windows 11, version 26H1 (28000.2704) amd64
Select language for Windows 11, version 26H1 (28000.2704) amd64 on UUP dump. UUP dump lets you download Unified Update Platform files, like Windows Insider updates, directly from Windows Update.
uupdump.net
UUP Dump - Download Windows Insider ISO
UUP Dump is the most practical and easy way to get ISO images of any Insider Windows 10 or Windows 11 version, as soon as Microsoft has released a new build. UUP Dump creates a download configuration file according to your choices, downloads necessary files directly from Microsoft servers, and...
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