Microsoft has released Windows 11 KB5121003 as part of the August 2026 Patch Tuesday rollout. Released on August 11, 2026, installing Windows KB5121003 update upgrades systems to Build 26200.9168 (25H2) and Build 26100.9168 (24H2).
In addition to monthly security updates, Windows 11 KB5121003 introduces several new features, along with important security and reliability improvements. According to Microsoft, the update addresses the latest security vulnerabilities, improves app launch performance on low-end PCs, adds typo-tolerant Windows Search, introduces Voice Access Voice Isolation, and expands Secure Boot certificate updates.
| Item | Details |
|---|---|
| Update | KB5121003 |
| Release Date | August 11, 2026 |
| OS Build | 26100.9168 (24H2), 26200.9168 (25H2) |
| Update Type | Cumulative Security Update |
| Available For | Windows 11 24H2 and 25H2 |
| Release Channel | August 2026 Patch Tuesday |
What’s New in Windows 11 KB5121003?
KB5121003 focuses mainly on quality improvements rather than introducing a major new Windows 11 feature. Some of the most useful changes include:
- Better Windows Search: Search can now handle typos and partial app names more effectively, while Settings search has been improved to surface more relevant results.
- File Explorer improvements: File sizes in Details view now use KB, MB, and GB units. You can also middle-click folders in the Address Bar and Home page to open them in a new tab. Microsoft has also fixed some display and scrolling problems.
- Voice Isolation: Voice Access gets a new Voice Isolation option designed to reduce background noise and interference from other speakers. Korean language support has also been added.
- New touchpad controls: Compatible precision touchpads now offer controls for scroll and zoom speed, along with accelerated scrolling to move through long documents faster.
- Windows Hello improvements: Enhanced Sign-in Security now supports peripheral fingerprint sensors on compatible systems.
- Widgets changes: Taskbar notification badges can now use the Windows accent color, while Weather becomes the only Lock screen widget shown by default for new users.
- Copilot+ PCs allow users to independently uninstall the Image Generation AI component to save storage and resources
- Windows Update improvements: Microsoft has improved update progress calculations and cleanup after installing updates. The update also restores the Energy Saver threshold setting under Power & Battery.
Microsoft notes that some of these changes are being rolled out gradually, so they may not appear on every PC immediately.
Secure Boot Certificate Update
KB5121003 also expands Microsoft’s ongoing Secure Boot certificate rollout.
The update includes additional high-confidence device-targeting data, increasing the number of supported devices that can automatically receive the newer Secure Boot certificates through Windows Update. Microsoft says the certificate deployment will continue across supported PCs and non-managed business devices in the coming months.
The update also includes Servicing Stack Update KB5123304, which brings the servicing stack to Build 26100.9156 and improves the reliability of installing Windows updates.
August 2026 Security Updates
Security remains the main reason to install KB5121003. Microsoft’s August 2026 Patch Tuesday release fixes more than 400 vulnerabilities, including three zero-day vulnerabilities. One of the zero-days, CVE-2026-68820, is actively exploited and affects the Windows Ancillary Function Driver for WinSock.
The other two publicly disclosed zero-days are CVE-2026-62832, affecting the Windows User Profile Service, and CVE-2026-72971, affecting the Windows Container Isolation FS Filter Driver.
For Windows 11 users, installing the August cumulative update ensures the latest available security protections are applied.
How to Download Windows 11 KB5121003
Windows 11 is a crucial security update that will be automatically downloaded and installed on devices with an active internet connection. You can also adjust Windows settings to delay the update by a week or two, but it’s generally not a good idea to delay security updates.
Alternatively, offline installers for Windows 11 KB5121003 are available on the Microsoft Update Catalog for manual installation in specific cases.
Also, you can manually download Windows 11 KB5121003 following the steps below:
- Press the Windows key + S, type settings, and select the first result.
- Go to Windows Update and check if the 2026-07 security update (KB5121003) (26200.9168).
- Click the Download Now button to begin the process.
- Once done, restart your computer to apply the changes.
Press the Windows key + R, type winver, and press Enter to check the latest build details.
Windows 11 KB5121003 offline installers
This patch is currently rolling out to everyone via Windows Update, but you can also download the offline installer for Windows 11 KB5121003 and install it manually. Here are the Windows 11 offline installer files you can download and install manually on your device.
- Windows 11 KB5121003 for version 25H2 Direct Download Links: 64-bit.
The file sizes are large, reflecting embedded AI models, with the x64 version being approximately 3.05 GB
Note: The link above opens the Microsoft Update Catalog, the library of Windows Update offline installers. Click the ‘Download’ button next to the OS version installed on your machine, then run the .msu files to start installing the update.
If you are looking for the latest Windows 11 ISO, click here.
Frequently Asked Questions
KB5121003 is the August 2026 cumulative security update for Windows 11 versions 24H2 and 25H2. It includes security fixes and improvements to several Windows components.
It does not introduce a major feature release, but it includes several new and improved experiences, including better Search, Voice Isolation, precision touchpad controls, File Explorer improvements, and Windows Update changes.
Yes. The update contains important security fixes, including protection against an actively exploited zero-day, along with several quality improvements.
You can install it through Settings > Windows Update or download the standalone package from the Microsoft Update Catalog.
Microsoft currently reports no known issues with the August 2026 update.
Source: Microsoft
