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What Is the Guaranteed Final Fix for Windows 11 Update KB5065426 Installation Errors?
The Windows 11 September 2025 Update, identified as KB5065426, is causing significant installation problems for some people. This is a mandatory security update for Windows 11 version 24H2, meaning your computer will try to install it automatically, but many are finding that the process repeatedly fails.
Users are encountering a range of issues. The update might get stuck during the download phase, taking an unusually long time to complete. More often, the installation process begins but then abruptly stops, rolling back any changes and displaying an error message. In addition to these installation failures, a smaller number of users who successfully install the update are reporting new problems with network file sharing. This article will provide a detailed guide on the problems, why common fixes are not working, and the most effective way to get your system updated correctly.
Common Installation Error Codes
When the KB5065426 update fails, Windows Update typically shows a specific error code. While these codes can point to different underlying causes, they are all leading to the same result for this particular update: a failed installation. The problem is not isolated to a single error; people are reporting a variety of codes, which indicates a complex issue with the update package itself rather than a simple problem on the user’s computer.
These problems are affecting a wide range of users, including those with years of experience managing Windows systems. It is not a matter of user error. Even system administrators who have never had issues with Windows Update before are finding themselves unable to apply this patch.
Here is a list of error codes that have been commonly associated with the failed September 2025 Update:
- 0x800F0991
- 0x800F0922
- 0x80071A2D
- 0x800F081F
- 0x80070302
- 0x80070306
- 0x8000FFFF
- 0x800700C1
The typical experience involves Windows Update downloading the package, attempting to install it, failing, and then presenting a “Retry” button. Clicking this button simply starts the same failed cycle over again. This loop can be persistent, as the system will continue trying to install this mandatory security patch during its regular checks.
Exploring Failed Workarounds
Experienced users often turn to a standard set of tools to fix update issues. However, for KB5065426, these routine methods are proving ineffective. This suggests the problem lies deeper than typical system file corruption or a glitch in the Windows Update service.
Many have tried using the System File Checker (SFC) and Deployment Image Servicing and Management (DISM) tools. These are command-line utilities designed to scan for and repair corrupted or missing Windows system files. Normally, running sfc /scannow followed by a DISM command can resolve stubborn update failures. In this case, users report that even after these tools complete successfully and find no issues, the KB5065426 update still refuses to install.
Another common workaround is to bypass the Windows Update service entirely. This involves manually downloading the update package from the Microsoft Update Catalog website. The catalog provides standalone installers for nearly all Windows updates. For this September patch, however, the manual method is also failing. People who have tried this find that the standalone installer begins, runs for a while, often reaching over half of the progress bar, and then suddenly closes. It provides a simple message stating that the update was not installed, often without giving a specific error code. This failure of the manual install further points to an issue within the update package itself.
A Step-by-Step Guide to a Successful Update
The most reliable method found so far to resolve the installation failures for KB5065426 is to perform an in-place upgrade using the Windows 11 Media Creation Tool. This tool is provided by Microsoft and is designed to upgrade a PC to the latest version of Windows or create installation media. When used for an in-place upgrade, it essentially reinstalls Windows 11 over your existing system. This process replaces core system files with fresh copies, which can resolve deep-seated issues that block updates, all while keeping your personal files, settings, and applications intact.
This method has the added benefit of fixing other potential hidden problems within the operating system. It’s a more comprehensive repair than standard troubleshooting tools can offer.
Follow these steps carefully to perform the in-place upgrade:
- Back Up Your Data. Before starting any major system process, it is always wise to back up your important documents, photos, and other personal files to an external drive or cloud service. While this process is designed to keep your files, unexpected errors can always occur.
- Download the Media Creation Tool. Navigate to the official Microsoft software download page for Windows 11. Find and download the Media Creation Tool.
- Run the Tool. Once downloaded, run the tool. You will need administrator privileges to proceed. Accept the software license terms when prompted.
- Choose the Upgrade Option. On the “What do you want to do?” screen, select the option “Upgrade this PC now.” Do not choose to create installation media. Click Next. The tool will then begin downloading the latest Windows 11 installation files. This can take some time depending on your internet connection speed.
- Confirm What to Keep. After the download is complete, you will reach the “Ready to install” screen. This screen will summarize your choices. It is critical that it says “Keep personal files and apps.” If this option is not selected or is grayed out, do not proceed. It could mean you have downloaded the wrong edition or language of the tool. In that case, cancel the installation and double-check your system’s version.
- Start the Installation. If everything looks correct, click the “Install” button. Your computer will now begin the in-place upgrade. It will restart several times during this process, which may take an hour or more to complete.
- Check for Updates. Once your PC has finished and you are back at your desktop, the KB5065426 update should now be installed. You can verify this by going to Settings > Windows Update > Update history. If it is not already there, a manual check for updates should now allow it to download and install smoothly.
As an alternative, the Windows 11 Installation Assistant can also perform an in-place upgrade and may work if the Media Creation Tool gives you trouble.
Issues After a Successful Update
For some, the problems do not end with installation. A number of users who were able to install KB5065426 have reported new issues. The most common post-update complaint involves network file sharing.
Users in home and small office environments have found that their ability to access shared folders on other Windows 11 computers across their local network is broken. Attempts to connect to a network share may fail with “System error 86” or result in repeated prompts for credentials that are not accepted. This issue appears to be directly linked to the update, as the functionality worked perfectly before its installation.
In a few isolated cases, people have also reported a complete loss of internet connectivity after the update. These reports are not widespread but are worth noting as a potential, though rare, side effect.
Uninstalling the September 2025 Update
If your computer is severely affected by issues like the file sharing bug after installing KB5065426, you may choose to uninstall it. Be aware that removing the update will also remove the security fixes it contains, leaving your system more vulnerable until a new, corrected patch is released. You will also lose any minor features it introduced, such as support for Emoji 16.
If you are within 10 days of installing the update, you can uninstall it with these steps:
- Open the Settings app.
- Navigate to the Windows Update section.
- Click on Update history.
- Scroll down and select Uninstall updates.
- In the list that appears, find the entry for KB5065426, select it, and click Uninstall.
Follow the prompts to complete the removal. If more than 10 days have passed, Windows may have removed the backup files, and the option to uninstall will be gone. In that situation, your only way to resolve the issues would be to perform an in-place upgrade with the Media Creation Tool, which would install a clean version of the system with the update already integrated.