Microsoft’s Windows 11 September 2026 Update has become a more significant release than a typical monthly security update.
The September 8 Patch Tuesday release, KB5124008, introduced security improvements and several quality fixes for Windows 11 24H2 and 25H2.
Microsoft subsequently released an out-of-band update, KB5129195, on September 14, 2026, to address several problems reported after the September security update, including Remote Desktop Services failures, Hyper-V Plan9 folder-sharing problems, and some USB audio issues.
There are also important Windows 11 feature changes arriving through gradual rollouts, including Start menu customization and taskbar improvements.
These features should not automatically be treated as part of the KB5124008 security package because Microsoft frequently rolls new Windows features out in phases.
In this guide, we’ll cover everything you need to know about the Windows 11 September 2026 Update, including KB numbers, build numbers, new features, security improvements, known problems, installation instructions, and what you should do if your PC is affected.
Windows 11 September 2026 Update at a Glance
| Detail | Information |
|---|---|
| September Patch Tuesday update | KB5124008 |
| KB5124008 release date | September 8, 2026 |
| KB5124008 — Windows 11 24H2 build | 26100.9445 |
| KB5124008 — Windows 11 25H2 build | 26200.9445 |
| September out-of-band update | KB5129195 |
| KB5129195 release date | September 14, 2026 |
| KB5129195 — Windows 11 24H2 build | 26100.9457 |
| KB5129195 — Windows 11 25H2 build | 26200.9457 |
| September update | KB5124010 |
| KB5124010 release date | September 22, 2026 |
| the October 13 security update | the October 13 security update |
| KB5124010 — Windows 11 24H2 build | 26100.9550 |
| KB5124010 — Windows 11 25H2 build | 26200.9550 |
| KB5124010 — Windows 11 26H2 build | 26300.9550 |
| Primary installation method | Windows Update |
| Manual installation | Microsoft Update Catalog |
Microsoft released three notable Windows 11 cumulative updates during September 2026. KB5124008 was the regular September 8 security update for Windows 11 24H2 and 25H2. KB5129195 followed on September 14 as an out-of-band cumulative update containing additional security and non-security improvements.
On September 22, Microsoft released KB5124010, a non-security preview cumulative update for Windows 11 24H2, 25H2, and 26H2. It is the newest September release, but it should not be described as the latest security update because it is a preview update.
For readers looking specifically for the September security updates, KB5124008 and KB5129195 are the important releases. Readers who installed the optional KB5124010 preview update will see the newer build numbers shown above.
What Is the Windows 11 September 2026 Update?
The Windows 11 September 2026 Update refers to several cumulative updates released by Microsoft during September 2026. The main September Patch Tuesday security update was KB5124008, released on September 8, 2026.
KB5124008 applies to Windows 11 version 24H2 and version 25H2. It brings Windows 11 24H2 to build 26100.9445 and Windows 11 25H2 to build 26200.9445.
Microsoft then released KB5129195 on September 14 as an out-of-band (OOB) cumulative update for Windows 11 24H2 and 25H2. It includes updates from previous releases along with additional security and non-security improvements.
KB5129195 raises the builds to:
- Windows 11 24H2: 26100.9457
- Windows 11 25H2: 26200.9457
Microsoft also released KB5124010 on September 22, 2026. This is a non-security preview cumulative update for Windows 11 24H2, 25H2, and 26H2. It is the newest September 2026 Windows 11 release, although it should not be confused with the month’s security update.
KB5124010 raises the builds to:
- Windows 11 24H2: 26100.9550
- Windows 11 25H2: 26200.9550
- Windows 11 26H2: 26300.9550
The preview update includes several feature and quality improvements, including File Explorer changes, Emoji 17.0 support, Bluetooth improvements, new precision touchpad gestures, Copilot key remapping, accessibility improvements, and a fix for the File History issue.
September 2026 Security Update vs. Optional Preview Update
| Date | Update | Type | Latest builds |
|---|---|---|---|
| September 8, 2026 | KB5124008 | Security | 24H2: 26100.9445 / 25H2: 26200.9445 |
| September 14, 2026 | KB5129195 | Out-of-band cumulative | 24H2: 26100.9457 / 25H2: 26200.9457 |
| September 22, 2026 | KB5124010 | Non-security preview | 24H2: 26100.9550 / 25H2: 26200.9550 / 26H2: 26300.9550 |
Microsoft released two important Windows 11 updates in September 2026, but they serve different purposes.
September 8, 2026 — KB5124008 (Security Update)
This monthly cumulative update delivered security protections and quality improvements for Windows 11 versions 24H2 and 25H2. It also included changes related to Secure Boot certificates, mouse customization, desktop personalization, and other Windows components. Some users subsequently encountered issues involving domain trust, USB audio, File History, and virtual machine folder sharing.
September 14, 2026 — KB5129195 (Out-of-band Update)
Microsoft released this update outside its normal monthly schedule to address urgent problems, including Remote Desktop Services instability. It also resolved or mitigated other issues affecting supported Windows versions.
September 22, 2026 — KB5124010 (Optional Non-security Preview)
This optional cumulative preview provided quality improvements before their planned inclusion in a later monthly update. It was also associated with a reported AC-3 audio compatibility issue and Remote Desktop connection failures in certain managed environments.
Which update should you install?
For most users, prioritize the latest applicable security update offered through Windows Update. Optional previews are intended for users who want early access to non-security fixes and improvements; installing one is not generally necessary to stay protected by the monthly security release. Before installing either type, review Microsoft’s current release-health documentation for issues affecting your Windows version and hardware.
Windows 11 September 2026 KB Numbers and Build Numbers
Microsoft released several cumulative updates for Windows 11 during September 2026. The main security update was KB5124008, followed by the out-of-band KB5129195 update. Microsoft also released KB5124010 as a non-security preview update later in the month.
KB5124008
KB5124008 was released on September 8, 2026, as the regular monthly cumulative security update for Windows 11 versions 24H2 and 25H2.
| Windows 11 version | Architecture | Build |
|---|---|---|
| 24H2 | x64 | 26100.9445 |
| 24H2 | ARM64 | 26100.9445 |
| 25H2 | x64 | 26200.9445 |
| 25H2 | ARM64 | 26200.9445 |
The update included security improvements along with fixes for issues affecting Microsoft Teams and Outlook on some Arm64 PCs, desktop personalization, mouse cursor customization, and other Windows components.
KB5129195
KB5129195 was released on September 14, 2026, as an out-of-band (OOB) cumulative update for Windows 11 24H2 and 25H2.
| Windows 11 version | Build after KB5129195 |
|---|---|
| Windows 11 24H2 | 26100.9457 |
| Windows 11 25H2 | 26200.9457 |
Microsoft describes KB5129195 as a cumulative update that includes previous releases along with additional security and non-security improvements. It also added protections related to CVE-2026-62721 and resolved several September update problems, including Remote Desktop Services instability and Hyper-V Plan9 host-folder sharing issues.
KB5124010
KB5124010 was released on September 22, 2026, as a non-security preview cumulative update. It is newer than KB5129195, so it should be included when describing all September 2026 Windows 11 updates.
| Windows 11 version | Build after KB5124010 |
|---|---|
| Windows 11 24H2 | 26100.9550 |
| Windows 11 25H2 | 26200.9550 |
| Windows 11 26H2 | 26300.9550 |
KB5124010 includes production-quality improvements and fixes rather than the month’s regular security patches. Among other changes, Microsoft says it addresses the File History backup problem introduced by the September security update.
Important: KB5124010 is a preview update, so it should not be described as the latest September security update. For 24H2 and 25H2, KB5129195 remains the September out-of-band security update, while KB5124010 is the newer non-security preview release.
Latest Windows 11 September 2026 Update: KB5124010
Microsoft released another Windows 11 update on September 22, 2026. The update, KB5124010, is a non-security preview cumulative update available for Windows 11 versions 26H2, 25H2, and 24H2.
Unlike KB5124008 and KB5129195, KB5124010 is a preview update, so it is primarily intended to deliver production-quality improvements and fixes before they are included in a future mandatory security update.
The September 22 update changes the Windows 11 builds to:
| Release | Date | Windows 11 version | Build |
|---|---|---|---|
| KB5124008 | Sept. 8, 2026 | 24H2 | 26100.9445 |
| KB5124008 | Sept. 8, 2026 | 25H2 | 26200.9445 |
| KB5129195 | Sept. 14, 2026 | 24H2 | 26100.9457 |
| KB5129195 | Sept. 14, 2026 | 25H2 | 26200.9457 |
| KB5124010 Preview | Sept. 22, 2026 | 24H2 | 26100.9550 |
| KB5124010 Preview | Sept. 22, 2026 | 25H2 | 26200.9550 |
| KB5124010 Preview | Sept. 22, 2026 | 26H2 | 26300.9550 |
Windows 11 24H2 Home and Pro reached end of support on October 13, 2026. Users on these editions should move to a supported Windows release to continue receiving security updates. Enterprise and Education editions have different servicing timelines, so check the lifecycle for your specific edition.
What’s New in KB5124010?
The September 22 preview update contains a substantial collection of improvements, including:
- File Explorer improvements, KB5124010 improves the File Explorer preview pane, preserves expanded/collapsed sections in File Explorer Home, improves cloud-file thumbnails and reorganizes information in the Details pane.
- Emoji 17.0 support, The September 22 preview update adds Emoji 17.0 support, including new emoji and refinements to several existing emoji. Users can open the emoji panel with Windows +
- A new Tips widget for the Windows Widgets board and lock screen.
- Improved desktop background and personalization reliability.
- Better Bluetooth Support: Microsoft has made several Bluetooth improvements, including better connection-state reporting, improved Bluetooth Settings reliability, microphone compatibility improvements, better LE Audio reliability and a fix for a Bluetooth audio crash.
- A new Open apps maximized accessibility option.
- A refreshed Magnifier toolbar.
- Improved Settings behavior and app version visibility.
- New Precision Touchpad Gestures: KB5124010 adds additional precision touchpad gestures. Users can enable single-finger edge scrolling and automatic scrolling from Settings > Bluetooth & devices > Touchpad.
- The ability to remap the Copilot key to Right Ctrl or the Context Menu key.
- Camera Roll backup in Settings for eligible users using OneDrive.
- Improvements to Windows Recovery and kiosk-mode behavior.
- Power and battery improvements on some plugged-in laptops.
Microsoft says some of these features use a gradual rollout, so they may not appear on every PC immediately.
File Explorer Improvements
KB5124010 improves the File Explorer preview pane, preserves expanded/collapsed sections in File Explorer Home, improves cloud-file thumbnails and reorganizes information in the Details pane.
Emoji 17.0 Support
The September 22 preview update adds Emoji 17.0 support, including new emoji and refinements to several existing emoji. Press Windows + . (period) to open the emoji panel.
Better Bluetooth Support
Microsoft has made several Bluetooth improvements, including better connection-state reporting, improved Bluetooth Settings reliability, microphone compatibility improvements, better LE Audio reliability and a fix for a Bluetooth audio crash.
New Precision Touchpad Gestures
KB5124010 adds additional precision touchpad gestures. Users can enable single-finger edge scrolling and automatic scrolling from Settings > Bluetooth & devices > Touchpad.
Remap the Copilot Key
A new Windows 11 setting allows supported Copilot-key keyboards to remap the key to Right Ctrl or the Context Menu key. This can help users preserve familiar keyboard shortcuts.
New “Open Apps Maximized” Accessibility Option
Windows 11 now includes an accessibility setting that automatically opens applications maximized. Microsoft says it is available under Settings > Accessibility > Visual effects.
Is KB5124010 a Security Update?
No. KB5124010 is a non-security preview cumulative update.
Users who want only security and stability updates can wait for the next regular cumulative security release. Users who want the latest fixes and production-quality improvements can install the preview update when it is offered through Windows Update.
The September 22 preview update is particularly relevant to this article because it represents the latest September 2026 Windows 11 release.
What’s New in the Windows 11 September 2026 Update?
The September release includes a mixture of security fixes, reliability improvements, and changes that are being rolled out separately through Microsoft’s normal feature-delivery process.
1. Security Improvements
- The September 8 update provides security improvements for Windows 11.
- Microsoft also included additional protection in the September 14 out-of-band update for CVE-2026-62721, a Windows User-Mode Power Service elevation-of-privilege vulnerability.
- For users, the main takeaway is that the September update is not simply a cosmetic Windows update. It includes security protections that are important for supported Windows 11 installations.
2. Fix for Microsoft Teams and Outlook on ARM PCs
- Microsoft resolved an issue affecting some ARM-based Windows 11 PCs where Microsoft Teams and the new Outlook for Windows could fail to launch or close unexpectedly after an earlier August security update.
- The issue is listed as resolved through KB5124008.
- If you’re using a Snapdragon-based or other ARM Windows 11 computer, installing the applicable current cumulative update is particularly relevant.
3. Fix for Desktop Background Problems
- Some Windows 11 systems affected by the August 27 update could lose their desktop background settings and display a solid black background.
- Microsoft lists this issue as resolved by KB5124008.
4. Fix for Mouse Customization Problems
- Microsoft also resolved an issue where custom cursors and cursor animations could intermittently revert on some non-English Windows installations.
- KB5124008 resolved this problem.
Windows 11 Start Menu Improvements
One of the more interesting Windows 11 developments around the September 2026 update cycle is the continued rollout of Start menu customization.
Microsoft’s Windows Insider documentation describes several Start menu improvements, including
- A choice between a small and large Start menu.
- An automatic size option.
- Renaming the Recommended section to Recent.
- The ability to hide your name and profile picture.
- Separate controls for Pinned, Recent, and All sections.
- Additional Start menu personalization controls.
Microsoft introduced these features through preview builds and gradual rollouts, meaning availability can vary between devices.
Therefore, users should not assume that every Windows 11 PC receiving KB5124008 will immediately show all of these options.
Windows 11 Taskbar Improvements
Microsoft is also continuing to expand taskbar customization.
Recent Windows 11 preview documentation describes additional taskbar customization and improved discoverability of taskbar settings. Microsoft says gradual rollouts can cause features to appear on devices at different times.
Some reports have also highlighted additional taskbar positioning and sizing changes. However, feature availability depends on the specific Windows build and rollout status.
If you’re writing about a particular taskbar feature, verify it against Microsoft’s release notes for the exact Windows 11 build rather than assuming that it is included in KB5124008.
Windows Search Improvements
Windows Search is also receiving usability improvements through Microsoft’s ongoing Windows development process.
Microsoft has described improvements intended to make Search more dependable, easier to scan, and clearer before a user selects a result.
Some search-related changes are part of gradual feature rollouts rather than the core security update itself.
Windows 11 September 2026 Update Known Issues
This is one of the most important sections for anyone installing the September update.
Microsoft’s Windows release health documentation has been updated several times since the September 8 security update. Some problems have been resolved by KB5129195 or later updates, while others remain mitigated or under investigation.
The current status is important because the situation has changed since the original KB5124008 release.
1. Remote Desktop Services Problems — Resolved
The September 8 update caused Remote Desktop Services problems in some organizations.
Symptoms included:
- RDP connections failing after several minutes.
- Sign-in problems.
- Servers becoming unresponsive during Remote Desktop configuration.
- Microsoft Management Console becoming unresponsive.
- RDS Licensing Diagnoser problems.
- File Explorer becoming unresponsive.
- Windows Update pages becoming stuck loading.
Microsoft resolved this issue with KB5129195, released September 14, 2026.
If your organization experienced these problems, install the latest applicable Windows update rather than continuing to troubleshoot the original KB5124008 installation.
2. USB Audio Problems — Partially Resolved
Some USB Audio Class 1.0 devices can fail to start or produce no sound after the September 8 update.
Possible symptoms include:
- Code 10 errors in Device Manager.
- No audio output.
- Unresponsive volume controls.
- Sound settings becoming unavailable.
- Problems with multichannel audio.
KB5129195 resolved the symptoms affecting 8-channel and 3D audio modes, but Microsoft says other USB Audio Class 1.0 symptoms remain under investigation.
If you depend on a USB audio interface, DAC, headset, or other USB Audio Class 1.0 device, check Microsoft’s latest release health information before troubleshooting.
3. Hyper-V Linux VM Folder Sharing — Resolved
KB5124008 caused problems with Plan9 host-folder sharing in some Hyper-V-based Linux virtual machines.
The virtual machine could start normally, but folders shared from the Windows host might not appear or could be inaccessible inside the Linux guest.
Microsoft resolved the problem with KB5129195.
Microsoft specifically identified applications such as Windows Subsystem for Linux (WSL) and Claude Cowork as potentially affected when they use the relevant Plan9 folder-sharing functionality.
4. Domain Trust Relationship Problems — Mitigated
Microsoft is investigating an issue affecting some domain-joined devices using Credential Guard-protected machine accounts.
After installing KB5124008 or later updates, affected devices can lose their secure channel with an on-premises Active Directory domain. Users may then be unable to sign in interactively with valid domain credentials and may see a message saying that the trust relationship between the device and domain failed.
Microsoft currently lists this issue as mitigated, rather than resolved.
The problem is primarily relevant to enterprise-managed Windows devices. Microsoft says it is related to Machine Identity Isolation settings in environments that are not using a supported Windows Server 2025 domain functional level.
5. File History Problems — Fixed by KB5124010
The September updates caused File History to fail on some Windows 11 systems.
Affected users could see a “Reconnect your drive” message even when a compatible external or network backup location was connected.
Microsoft addressed this problem in KB5124010, the September 22, 2026 non-security preview update.
If File History is important to you, install the applicable update and verify that your backups are running normally rather than assuming the problem has disappeared automatically.
6. Black Screen or Desktop Loading Problems — Mitigated
Microsoft added another known issue in late September involving some virtual desktop environments.
Some devices, particularly certain Azure Virtual Desktop hosts using FSLogix, may display a black screen after sign-in or fail to load the desktop automatically.
Microsoft currently lists this issue as mitigated.
Affected enterprise users may temporarily launch explorer.exe manually, while Microsoft has also provided a Known Issue Rollback mechanism for managed environments. Microsoft says a permanent resolution is planned for a future Windows update.
7. Microsoft Defender “Turned Off” Notifications — Resolved
Some users could receive incorrect notifications saying that Microsoft Defender Antivirus was turned off even though Defender remained active.
Microsoft resolved this issue through a Microsoft Defender Antivirus update released on September 17, 2026.
Therefore, this should not be listed as an active Windows 11 September update problem.ur backup configuration is working normally after installing the September update.
September 2026 Out-of-Band Update KB5129195
What Is KB5129195?
KB5129195 is an emergency, or out-of-band, cumulative update released by Microsoft on September 14, 2026.
It applies to Windows 11 24H2 and 25H2 and updates the operating system to builds 26100.9457 and 26200.9457, respectively.
Microsoft says KB5129195 includes:
- Security protection for CVE-2026-62721.
- A fix for Remote Desktop Services problems.
- A fix for Hyper-V Plan9 host-folder sharing problems.
- A partial fix for USB audio issues.
- Previous cumulative updates.
Should You Install KB5129195?
If you’re running Windows 11 24H2 or 25H2 and Windows Update offers KB5129195, it is the current September out-of-band cumulative update and includes important fixes.
Users who experienced RDP, Hyper-V folder-sharing, or certain USB audio problems should pay particular attention to this update.
Windows 11 24H2 End of Support Is Coming
There is another important reason for Windows 11 24H2 users to pay attention to their Windows version.
Microsoft states that Windows 11 version 24H2 Home and Pro editions reach the end of updates on October 13, 2026.
After that date, those editions will no longer receive monthly security and preview updates, fixes for known issues, time zone updates, or technical support.
Enterprise and Education editions of Windows 11 24H2 remain supported until October 12, 2027.
If you’re using Windows 11 24H2 Home or Pro, check Windows Update for an available newer Windows 11 version before the October deadline.
Windows Secure Boot Certificate Updates
Microsoft is also continuing its Secure Boot certificate transition.
Microsoft says Secure Boot certificates used by many Windows devices began expiring in June 2026. Microsoft has been deploying newer certificates to PCs and unmanaged business devices through Windows Update. Devices that have not yet received the new certificates will continue to start, and normal Windows updates will continue to install.
Microsoft says certificate deployment will continue through Windows Updates in the coming months.
For most users, there is no need to manually change Secure Boot settings simply because of this notice. Keep Windows updated and follow Microsoft’s guidance if your device receives a specific Secure Boot certificate notification.
How to Install the Windows 11 September 2026 Update
The easiest way to install the latest September update is through Windows Update.
Install Windows 11 Updates Through Settings
- Press Windows + I to open Settings.
- Select Windows Update.
- Click Check for updates.
- Allow Windows to search for available updates.
- Download and install the available cumulative update.
- Restart your computer when prompted.
- Return to Windows Update and check again if necessary.
Microsoft says KB5124008 and KB5129195 are available through Windows Update, Windows Update for Business, and the Microsoft Update Catalog.
How to Download the Windows 11 September 2026 Update Manually
If Windows Update does not offer the September 2026 update, you can download the required package manually from the Microsoft Update Catalog.
For users who specifically want the September 2026 out-of-band security update, search for KB5129195. Microsoft provides separate x64 and ARM64 packages for Windows 11 24H2 and 25H2.
Download KB5129195 Manually
- Open the Microsoft Update Catalog.
- Search for KB5129195.
- Find the package matching your Windows 11 version and processor architecture.
- Select the appropriate x64 or ARM64 package.
- Download the
.msufile. - If Microsoft lists a required checkpoint cumulative update, download that package as well.
- Install the required checkpoint update first, followed by KB5129195.
- Restart your PC if Windows requests it.
Microsoft’s documentation notes that the Update Catalog may list one or more required checkpoint cumulative updates alongside the target cumulative update. These checkpoint updates must be installed in the required order before the target update.
Which KB5129195 Package Should You Download?
| Windows 11 version | Architecture | Build after KB5129195 |
|---|---|---|
| Windows 11 24H2 | x64 | 26100.9457 |
| Windows 11 24H2 | ARM64 | 26100.9457 |
| Windows 11 25H2 | x64 | 26200.9457 |
| Windows 11 25H2 | ARM64 | 26200.9457 |
The Microsoft Update Catalog currently lists the corresponding x64 and ARM64 packages for Windows 11 24H2 and 25H2.
What About KB5124010?
If you want to manually install the newest September 2026 preview update, search the Microsoft Update Catalog for KB5124010 instead.
KB5124010 is a non-security preview cumulative update released on September 22, 2026. It applies to Windows 11 24H2, 25H2, and 26H2 and raises the builds to:
| Windows 11 version | Build after KB5124010 |
|---|---|
| Windows 11 24H2 | 26100.9550 |
| Windows 11 25H2 | 26200.9550 |
| Windows 11 26H2 | 26300.9550 |
Microsoft provides separate x64 and ARM64 installation instructions for KB5124010 and notes that required checkpoint cumulative updates may need to be installed first.
Important: KB5124010 is an optional, non-security preview update. It should not be confused with KB5129195, which is the September 2026 out-of-band security update for Windows 11 24H2 and 25H2.
How to Check Your Windows 11 Version
Before installing or troubleshooting a Windows 11 update, check which Windows version and OS build your PC is currently running.
The easiest method is the winver command:
- Press Windows + R.
- Type
winver. - Press Enter.
- Check the Windows version and OS Build shown in the dialog box.
You can also check this information through:
Settings > System > About
Look under Windows specifications for your Windows edition, version, and OS build.
How to Check Whether KB5124008, KB5129195, or KB5124010 Is Installed
You can check your installed Windows updates through Windows Settings:
- Open Settings.
- Select Windows Update.
- Select Update history.
- Expand or review Quality Updates.
- Look for KB5124008, KB5129195, or KB5124010.
You can also use winver to check the OS build after an update has been installed.
For the September 2026 updates:
- 26100.9445 — Windows 11 24H2 after KB5124008
- 26200.9445 — Windows 11 25H2 after KB5124008
- 26100.9457 — Windows 11 24H2 after KB5129195
- 26200.9457 — Windows 11 25H2 after KB5129195
- 26100.9550 — Windows 11 24H2 after KB5124010
- 26200.9550 — Windows 11 25H2 after KB5124010
- 26300.9550 — Windows 11 26H2 after KB5124010
Microsoft’s Windows release information confirms the 24H2 and 25H2 builds associated with KB5124008 and KB5129195. KB5124010 is a later non-security preview update that applies to 24H2, 25H2, and 26H2.
What to Do Before Installing a Windows 11 Update
Windows updates are designed to preserve your personal files and installed applications, but it is still good practice to prepare your PC before installing a major or cumulative update.
- Back Up Important Files: Create a current backup of important documents, photos, videos, work files, and other data. Store the backup on an external drive, network location, or trusted cloud storage.
- Create a Restore Point: A restore point can provide another recovery option if an update causes a software or configuration problem. This is particularly useful before making other system changes.
- Check Available Storage: Make sure your Windows system drive has enough free space for the update and temporary installation files. If you need more space, see our guide on how to free up disk space on Windows 11.
- Check Important Drivers: If your PC uses specialized hardware, check whether important graphics, chipset, audio, network, or peripheral drivers have known compatibility issues with the Windows version you are installing. For most users, avoid installing unnecessary driver updates immediately before a Windows update unless there is a specific compatibility or hardware reason to do so.
- Check Microsoft’s Windows Release Health Information: Before troubleshooting a failed or problematic Windows update, check Microsoft’s current Windows release health documentation.
Windows 11 Release Health — Microsoft Learn
Microsoft uses the release health pages to document known issues, mitigations, resolutions, affected Windows versions, and update-specific information.
This is particularly useful for business PCs, workstations, virtual machines, domain-joined computers, and enterprise environments, where update-related compatibility issues can have a larger impact.
How to Fix Windows 11 September Update Problems
If your computer behaves differently after installing the September update, start with basic troubleshooting.
- Restart Your Computer: A restart can complete pending update operations and resolve temporary system problems.
- Check for Another Update: Microsoft may release additional fixes after a monthly update, as demonstrated by KB5129195. Open: Settings > Windows Update. Then select Check for updates.
- Update Your Drivers: If the problem involves audio, graphics, networking, USB devices, or other hardware, check for updated drivers.
- Run Windows Update Troubleshooter: Windows includes troubleshooting tools designed to identify common Windows 11 update problems.
- Use Windows Recovery Options: If a serious problem remains, Windows provides recovery options such as System Restore and uninstalling recent updates.
However, removing a security update should not be the first troubleshooting step unless there is a specific reason. Installing the latest cumulative fix is generally preferable when Microsoft has already addressed the problem.
Should You Install the Windows 11 September 2026 Update?
For most supported Windows 11 users, keeping Windows updated remains important because Microsoft’s September releases include security protections, bug fixes, and reliability improvements.
However, there are now three important September 2026 releases to distinguish:
- KB5124008 — September 8 security update.
- KB5129195 — September 14 out-of-band cumulative update that fixed several problems caused by the September security release.
- KB5124010 — September 22 non-security preview update containing additional fixes and production-quality improvements.
For most users, the important distinction is between security updates and preview updates.
Home Users
Home users who want the normal security-maintenance path should install the latest applicable security update offered through Windows Update.
If Windows Update offers KB5124010 as an optional preview update, you can install it if you want its additional fixes and features, but you do not need to install a preview update simply to receive the next month’s security protections.
Gamers
Gamers should keep Windows and graphics drivers updated.
If a game, controller, headset, Bluetooth accessory, or other peripheral behaves differently after an update, check Microsoft’s Windows release health information and the hardware manufacturer’s support documentation before assuming the Windows update is responsible.
Business Users
Organizations should test cumulative updates against important applications and infrastructure before broad deployment.
Particular attention should be given to:
- Active Directory environments.
- Credential Guard configurations.
- Remote Desktop Services.
- Hyper-V and Linux virtual machines.
- USB audio hardware.
- Specialized enterprise applications.
The September release is a good example of why staged deployment and release-health monitoring are useful for managed Windows environments.
ARM PC Users
ARM-based PC users should make sure they have the September updates installed because KB5124008 resolved an issue that could cause Microsoft Teams and the new Outlook for Windows to fail to launch or close unexpectedly on some ARM devices.
What About KB5124010?
KB5124010 is a preview update rather than a regular security update.
It is useful for users who want the latest production-quality fixes and improvements, including the File History fix, Bluetooth improvements, new touchpad gestures, Copilot key remapping, File Explorer changes, and other Windows 11 improvements.
Users who prefer a more conservative update strategy can wait for these changes to arrive through a future regular cumulative update.
Pros and Cons of the September 2026 Windows 11 Update
| Benefits | Considerations |
|---|---|
| Important security improvements | Some post-update issues were reported |
| Fixes several earlier Windows problems | Some features are gradually rolled out |
| Fixes RDP problems through KB5129195 | USB audio issue is only partially resolved |
| Fixes Hyper-V Plan9 sharing problems | Enterprise users should test updates |
| Includes additional vulnerability protection | Windows 11 24H2 Home/Pro support is ending soon |
Frequently Asked Questions (FAQs) on Windows 11 September 2026 Update
What is the Windows 11 September 2026 update?
The Windows 11 September 2026 update consists of several cumulative releases. KB5124008 was the regular September 8 security update, KB5129195 was released on September 14 as an out-of-band cumulative security update, and KB5124010 was released on September 22 as a non-security preview update.
What is the latest Windows 11 September 2026 update?
KB5124010 is the newest September 2026 Windows 11 release. Microsoft released it on September 22 as a non-security preview cumulative update. It applies to Windows 11 24H2, 25H2, and 26H2. However, KB5124010 is not a security update; KB5129195 remains the September out-of-band security update for 24H2 and 25H2.
What is the latest Windows 11 September 2026 security update?
For Windows 11 24H2 and 25H2, KB5129195 is the September 2026 out-of-band security update. It was released on September 14 and includes previous updates plus additional security and non-security improvements, including protections for CVE-2026-62721.
What build does KB5124008 install?
KB5124008 brings Windows 11 24H2 to build 26100.9445 and Windows 11 25H2 to build 26200.9445. The update was released on September 8, 2026, as the regular monthly security update. You can verify your installed build by running winver or checking Settings > System > About.
What build does KB5129195 install?
KB5129195 brings Windows 11 24H2 to build 26100.9457 and Windows 11 25H2 to build 26200.9457. It was released on September 14, 2026, as an out-of-band cumulative update.
What build does KB5124010 install?
KB5129195 partially resolves the USB Audio Class 1.0 problem introduced by KB5124008. The OOB update fixes symptoms associated with 8-channel and 3D audio modes. Microsoft says other USB audio symptoms remain under investigation, so users experiencing continuing problems should check the latest release health information.
Does KB5124010 fix the File History problem?
Yes. Microsoft says KB5124010 fixes an issue that could prevent File History from backing up or restoring files to an external drive or network location. Affected systems could incorrectly display a “Reconnect your drive” message even when the backup drive was connected and working.
Did KB5129195 fix the Remote Desktop problem?
Yes. Microsoft lists the Remote Desktop Services instability introduced by the September security update as fixed by KB5129195. The issue could cause RDP connection or sign-in failures and, in some environments, cause servers to become unresponsive during Remote Desktop configuration.
Are there any known issues with the Windows 11 September 2026 updates?
Yes. Microsoft continues to track some September issues. These include problems involving USB Audio Class 1.0 devices, certain domain-joined devices with Credential Guard-protected machine accounts, and desktop-loading or black-screen problems in some virtual desktop environments. Microsoft has marked some issues as mitigated while others remain under investigation.
Is KB5124010 a security update?
No. KB5124010 is a non-security preview cumulative update. It contains production-quality improvements and fixes and is optional compared with the regular monthly security update. Microsoft describes it as the final preview update for Windows 11 24H2. Windows 11 24H2 Home and Pro will continue receiving monthly security updates until October 13, 2026.
How do I install the Windows 11 September 2026 update?
The normal method is Settings > Windows Update > Check for updates. You can also manually download cumulative update packages through the Microsoft Update Catalog. For manual installation, Microsoft notes that the Catalog may provide required checkpoint cumulative updates that need to be installed in the specified order before the target update.
How do I check if KB5124008 or KB5129195 is installed?
Open Settings > Windows Update > Update history and review the installed quality updates. Search for KB5124008 or KB5129195. You can also run winver to check the resulting OS build. For example, build 26100.9457 indicates Windows 11 24H2 after KB5129195, while 26200.9457 indicates Windows 11 25H2 after that update.
Final Thoughts on Windows 11 September 2026 Update
The Windows 11 September 2026 Update is more than a single KB package. Microsoft released several cumulative updates during the month, including the September security update, an out-of-band update, and a later non-security preview update.
The September 8 KB5124008 update delivered the month’s main security improvements for Windows 11 24H2 and 25H2. Microsoft then released KB5129195 on September 14 as an out-of-band cumulative update, adding security protections and resolving issues including Remote Desktop Services instability and Hyper-V Plan9 host-folder sharing problems.
Microsoft subsequently released KB5124010 on September 22 as a non-security preview cumulative update for Windows 11 24H2, 25H2, and 26H2. It includes additional feature, quality, and reliability improvements, and Microsoft says it resolves the File History backup problem associated with the September security update.
For most users, the important step is to make sure Windows is running the latest applicable update offered for their device, rather than stopping at the original September 8 build.
If you’re running Windows 11 24H2 Home or Pro, there is another deadline to keep in mind: Microsoft says those editions reach end of updates on October 13, 2026.
Windows 11 users should therefore check their current version and build, install applicable updates, and review Microsoft’s Windows release health documentation if they encounter update-related problems.
For TechyDen readers, this article should continue to be updated when Microsoft changes the status of known issues or publishes additional information about the September 2026 updates.
Windows 11 September 2026 Update: Quick Summary
- KB5124008: September 8, 2026 security update for Windows 11 24H2 and 25H2.
- KB5129195: September 14, 2026 out-of-band cumulative security update for 24H2 and 25H2.
- KB5124010: September 22, 2026 non-security preview cumulative update for 24H2, 25H2, and 26H2.
- KB5124008 builds: 26100.9445 for 24H2 and 26200.9445 for 25H2.
- KB5129195 builds: 26100.9457 for 24H2 and 26200.9457 for 25H2.
- KB5124010 builds: 26100.9550 for 24H2, 26200.9550 for 25H2, and 26300.9550 for 26H2.
- File History: The backup problem that could produce a “Reconnect your drive” message is resolved by updates released from September 22, including KB5124010.
- Remote Desktop Services: The September RDP instability issue is resolved by KB5129195.
- Hyper-V Plan9 folder sharing: The issue is resolved by KB5129195.
- USB Audio Class 1.0: Some symptoms were resolved by KB5129195, but remaining problems are still listed as mitigated and under investigation.
- Domain trust issue: The Credential Guard/domain secure-channel problem is currently mitigated and remains under investigation.
- Black screen/desktop loading: The issue is currently mitigated in some virtual desktop environments.
- Microsoft Defender notifications: Incorrect notifications stating that Microsoft Defender Antivirus was turned off have been resolved.
- Windows 11 24H2 Home/Pro: End of updates is scheduled for October 13, 2026.
- KB5124010 improvements: Includes File Explorer, Bluetooth, touchpad, accessibility, Copilot-key, Emoji 17.0, personalization, and other quality improvements.
Current Status
As of September 30, 2026, KB5124010 is the latest September 2026 Windows 11 cumulative preview update. KB5129195 remains the September out-of-band security release for Windows 11 24H2 and 25H2, while KB5124010 is newer but non-security.
This distinction is important because someone searching for the latest Windows 11 September 2026 update may be looking for the newest cumulative release, while someone searching for the latest September security update is looking for KB5129195.
Microsoft also reports that Windows 11 version 26H2 reached general availability on September 29, 2026, with the rollout occurring in phases on eligible 24H2 and 25H2 devices.
