Microsoft has released Windows 11 KB5124008 as part of the September 2026 Patch Tuesday update. The update is available for Windows 11 version 24H2 and version 25H2 and brings the OS builds to 26100.9445 and 26200.9445, respectively. Today’s updates mainly focus on bug fixes and security improvements. Microsoft has also introduced several noticeable changes to the Windows interface, including more control over the Taskbar and Start menu, a redesigned Windows Search experience, improvements to Windows Search, File Explorer, Windows Share, and several other areas.
The September update is also important from a security perspective. Microsoft’s September 2026 security release addresses around 1,000 vulnerabilities, including two actively exploited zero-day flaws.
Note: Microsoft is rolling out some new features gradually through Controlled Feature Rollout (CFR), so they may not appear on every Windows 11 device immediately after installing KB5124008.
Let’s take a closer look at what’s new in Windows 11 KB5124008.
| Update Summary | Details |
|---|---|
| KB Number | KB5124008 |
| Build Numbers | 26200.9445 (25H2) / 26100.9445 (24H2) |
| Release Date | September 08, 2026 |
| Update Type | Security Update (Patch Tuesday) |
| Primary Focus | Security Fixes, Quality Improvements, New Features |
| Major changes | Taskbar, Start menu, Search, File Explorer, Windows Share |
| Installation Required | Recommended |
| Restart Required | Yes |
What’s New in Windows 11 KB5124008 Update?
The September 2026 update includes several changes that Windows 11 users will notice after installing the update. Some features are being delivered gradually through Microsoft’s controlled feature rollout, so they may not appear on every PC immediately.
1. You Can Finally Move the Windows 11 Taskbar
One of the biggest changes in KB5124008 is the return of Taskbar positioning options. Windows 11 users can now choose whether the Taskbar appears at the bottom, Top, left, or right. This is a significant change because Windows 11 originally restricted the Taskbar to the bottom of the screen by default.
Microsoft says most Taskbar customization features continue to work when the Taskbar is moved, including options such as never combining Taskbar icons. However, some features have limitations. For example, the Search box and smaller Taskbar option currently support only the top and bottom positions.
You can find the setting under: Settings > Personalization > Taskbar > Taskbar behaviors > Taskbar position.
2. Windows 11 Gets a Smaller Taskbar
KB5124008 also adds a smaller Taskbar option. This reduces the Taskbar’s height and the size of its icons, giving users more usable screen space. This could be particularly useful on laptops and smaller displays.
To change the setting, go to: Settings > Personalization > Taskbar > Taskbar behaviors > Taskbar size
Select Small to reduce the Taskbar size.
Microsoft has also expanded the Taskbar behaviors section by default, making these customization options easier to discover.
3. More Start Menu Customization
Microsoft is also giving the Windows 11 Start menu more flexibility. KB5124008 adds options to change the size of the Start menu. Users can select: Automatic, Small, or Large.
You can find the setting under: Settings > Personalization > Start > Start menu size
The update also renames the Recommended section to Recent.
Microsoft has also redesigned the Start menu settings page. Users can independently control whether sections such as Pinned, Recent and All appear in Start. Another new option allows you to hide your name and profile picture from the Start menu.
This could be useful if you frequently share your screen during meetings or presentations.
4. Windows Search Gets Cleaner
KB5124008 also changes how Windows Search works. Microsoft is giving users more control over web and Microsoft Store suggestions, while making the Search experience less cluttered. The update also improves app discovery, including better handling of partial or misspelled app names.
The Search settings can be accessed from: Settings > Privacy & security > Search
Depending on the configuration and rollout status, users can control additional search behavior and suggested results.
5. File Explorer Should Feel Faster
Microsoft is also making some improvements to File Explorer. The Home page now launches faster and is more responsive, while the Recommended section gains touch-scrolling support on compatible devices.
These aren’t dramatic changes, but they should make everyday File Explorer use feel a little smoother.
6. Windows Gets a New Loading Spinner
KB5124008 introduces updated progress indicators across Windows 11. The refreshed animation appears in areas such as: Startup, Sign-in, Restart, Shutdown and Windows Update installation.
The goal is mainly to make these older interface elements look more consistent with the rest of Windows 11.
Microsoft is also improving the Windows Share experience. Users signed in with a work or school account can discover and install relevant applications directly from the Share window.
The setting is available under: Settings > System > Share > Show suggested apps in share surfaces
This is primarily useful in managed work and school environments.
8. Administrator Protection Begins Rolling Out
One of the more important security-related changes is the beginning of Microsoft’s Administrator Protection rollout. The feature is designed to reduce the amount of time administrators operate with elevated privileges. Instead of allowing administrator privileges to remain freely available, it uses just-in-time elevation for administrative tasks.
Microsoft says Administrator Protection is disabled by default and can be enabled through Microsoft Intune using OMA-URI or through Group Policy. This feature is more relevant to organizations and managed Windows environments than to typical home users.
9. WMIC Is No Longer Included
Another important change concerns the legacy Windows Management Instrumentation Command-line (WMIC) utility. Windows 11 24H2 and 25H2 no longer include WMIC as an optional Feature on Demand. The change affects the wmic.exe command-line utility, not the underlying Windows Management Instrumentation technology itself.
If you still have older scripts or tools that rely on WMIC commands, you may need to update them to use PowerShell or other supported WMI interfaces.
Other Improvements and Fixes
KB5124008 also includes several smaller fixes and improvements across Windows 11:
- Windows Networking: Fixes issues that could affect network connectivity and reliability.
- VPN: Improves VPN connectivity and addresses problems that could cause connections to fail or behave unexpectedly.
- Japanese IME: Fixes issues affecting the Japanese Input Method Editor when typing or switching input modes.
- Touchpad: Improves touchpad reliability and responsiveness on supported devices.
- Taskbar: Fixes problems affecting icons and the system tray.
- Windows Share: Addresses issues with sharing files and content from Windows.
- Task Manager: Fixes issues that could affect its behavior or display.
- Windows Update: Includes improvements to the Windows Update and servicing process.
- Graphics: Addresses several graphics-related problems affecting Windows and supported hardware.
- Improves keyboard and other text input behavior.
- Cryptography: Includes security and reliability improvements to Windows cryptographic components.
- Remote Management: Fixes issues affecting remote administration and management features.
- Windows Setup: Includes improvements that make Windows installation and servicing more reliable.
- Secure Boot: Adds more device-targeting data to expand coverage for PCs eligible to receive the new Secure Boot certificates through Windows Update.
- Mouse: Fixes an issue where customized mouse pointer styles and colors might not display correctly.
- Personalization: Fixes a problem that could cause the desktop background and other personalization settings to fail to load, sometimes resulting in a black desktop.
- Teams and Outlook: Fixes an issue that could cause Microsoft Teams and Outlook to unexpectedly close on Arm64 PCs.
- Date and Time: Updates Morocco Standard Time to reflect the country’s transition to permanent UTC+00:00 on September 20, 2026.
- Remote Desktop Audio: Fixes an issue where audio redirected from a Remote Desktop session might not play on the local device.
- OMA-DM Logging: Improves diagnostic logging for the OMA-DM client, making it easier to troubleshoot device management server connection issues.
Security Fixes in Windows 11 KB5124008
KB5124008 includes the September 2026 security fixes for Windows 11 24H2 and 25H2. Independent security tracking counted 966 vulnerabilities in Microsoft’s Patch Tuesday release, including two actively exploited Windows zero-days.
The two exploited flaws, CVE-2026-81963 and CVE-2026-85880, are elevation-of-privilege vulnerabilities affecting Windows components. Since both were already being exploited, installing KB5124008 is especially important.
Microsoft recommends installing KB5124008 as soon as possible to receive the latest security protections, reliability improvements, and bug fixes.
How to Install Windows 11 KB5124008 Update
KB5124008 is available through Windows Update, Microsoft Update, and the Microsoft Update Catalog. On most PCs, it will download and install automatically.
If you want to check manually:
- Press the Windows key + X, then select Settings. Go to Windows Update, then click Check for updates.
- You should see the September 2026 cumulative update (KB5124008) (26200.9445) available for download.
- Click on the Download Now button to begin the process. Once done, reboot your computer to apply the changes.
- Windows 11 KB5124008 download offline installer
- Windows 11 KB5122880 download offline installer
The link above points to the Microsoft Update Catalog, a library of Windows Update offline installers.
- First, click on the ‘Download’ button next to the version of the OS installed on your machine.
- Next, run the .msu files to install the update.
- Once done, reboot your PC to apply the changes.
After the installation is complete, press Windows + R, type winver, and press Enter.
You should see one of the following build numbers:
| Windows version | Build after installing |
|---|---|
| Windows 11 24H2 | 26100.9445 |
| Windows 11 25H2 | 26200.9445 |
If you don’t see the update immediately, it may still be rolling out to your device. You can also install it manually using the offline installer from the Microsoft Update Catalog.
Troubleshooting: Windows 11 KB5124008 Fails to Install
If KB5124008 won’t install, gets stuck while downloading, or shows an installation error, try the following solutions in order. In most cases, one of these methods resolves the problem.
1. Restart Your PC and Check for Updates Again
Temporary Windows Update glitches can sometimes prevent cumulative updates from installing correctly.
- Restart your computer.
- Open Settings > Windows Update.
- Click Check for updates and try installing KB5124008 again.
2. Run the Windows Update Troubleshooter
Windows includes a built-in troubleshooter that can automatically detect and fix common update problems.
- Open Settings.
- Go to System > Troubleshoot > Other troubleshooters.
- Click Run next to Windows Update.
- Apply any recommended fixes and restart your PC.
3. Check Your Internet Connection and Free Disk Space
A slow internet connection or insufficient storage can interrupt the installation process.
- Make sure your internet connection is stable.
- Ensure the C: drive has at least 10 GB of free space for Windows Update to download and install files.
- Remove temporary files or uninstall unused apps if necessary.
4. Repair Corrupted System Files
Corrupted Windows system files are a common reason cumulative updates fail.
Open Command Prompt as Administrator and run:
sfc /scannowAfter it finishes, run:
DISM /Online /Cleanup-Image /RestoreHealthRestart your PC and try installing the update again.
5. Temporarily Disable Third-Party Antivirus
Some third-party antivirus or firewall programs can interfere with Windows Update.
Temporarily disable your security software, install KB5124008, then re-enable protection after the installation finishes.
6. Install KB5124008 Using the Offline Installer
If Windows Update continues to fail, download the standalone installer from the Microsoft Update Catalog.
- Search for KB5124008.
- Download the package that matches your Windows version (24H2 or 25H2) and system architecture (x64 or ARM64).
- Double-click the downloaded .msu file.
- Restart your computer when prompted.
7. Note the Windows Update Error Code
If the installation still fails, check the error code shown in Windows Update (for example, 0x800f0922, 0x80070002, or 0x80073712). The error code usually points to the underlying cause and helps identify the correct solution.
Frequently Asked Questions
KB5124008 is the September 2026 Patch Tuesday cumulative update for Windows 11 versions 25H2 and 24H2. It includes important security fixes, quality improvements, and several new features designed to improve performance, accessibility, and overall system reliability.
Yes. KB5124008 is a mandatory security update released as part of Microsoft’s July 2026 Patch Tuesday. It includes security fixes, non-security improvements, and bug fixes.
After installing KB5124008, your Windows 11 version will be Build 26100.9445 (for 24H2) or Build 26200.9445 (for 25H2). You can confirm this by running winver.
Microsoft is using Controlled Feature Rollout (CFR) to gradually release some new features. As a result, certain features may not appear immediately on all devices even after the update is installed.
If the update won’t install, restart your PC and run the Windows Update Troubleshooter. If the problem continues, repair Windows system files using SFC and DISM, or install the update manually using the offline installer from the Microsoft Update Catalog. Checking the Windows Update error code can also help identify the cause of the problem.
Yes. You can uninstall it from Settings → Windows Update → Update history → Uninstall updates if you face any issues. However, uninstalling security updates is not recommended as a long‑term solution. Use it only for troubleshooting and reinstall the update when possible.
