Troubleshooting Windows 11 KB5065426 Installation Issues in September 2025 Update

Troubleshooting Windows 11 Update KB5065426 Installation Issues

The rollout of Windows 11 KB5065426 as part of the September 2025 update has been met with several installation challenges. Common error codes such as 0x800F0991, 0x800F0922, 0x80071A2D, and 0x800F081F among others, have been reported by users attempting to install the update. In addition, some users have noted that the update is taking significantly longer to download, likely due to its sizable data footprint or underlying glitches. Concerns have also been raised regarding file sharing functionalities, which seem disrupted post-update.

2025-09 Cumulative Update for Windows 11 Version 24H2 for x64-based Systems (KB5065426) (26100.6584)

What is KB5065426?

KB5065426 is an essential security patch associated with the Windows 11 September 2025 Update. Once included, it attempts installation at every system check for new updates. Despite its importance, numerous users have expressed frustration over the update’s failure to install, prompting a flurry of messages reporting the same.

Common Error Codes

One user shared that they encounter error 0x800F081F while attempting the installation. Unfortunately, this isn’t an isolated case. A range of error codes may appear, including:

0x800F0991
0x800F0922
0x80071A2D
0x800F081F
0x80070302
0x80070306
0x8000FFFF

Feedback indicates that a significant number of users are struggling with the update process. For instance, one user mentioned: “Despite using SFC and DISM commands to check for corrupted files, the installation fails repeatedly with a ‘retry all’ option leading to nothing but additional failure.” Another mentioned manual installation attempts ended with a generic “did not install”message, with no specific error reported.

Feedback from Experts

A seasoned system administrator also weighed in: “No matter what I try, KB5065426 just won’t install. This is unusual as I previously had no issues.” Curiously, many users who never faced problems with updates are now encountering multiple errors during this rollout.

One particularly frustrating instance reported an installation error of 0x800F0991, leaving even experienced users puzzled. The struggles are not unheard of, and it seems to be a widespread problem affecting a variety of users.

Alternative Installation Method: Microsoft Update Catalog

For those facing difficulties with Windows Update, the suggestion to use the Microsoft Update Catalog often arises. However, users have reported experiencing their own set of errors when attempting to install KB5065426 through this channel.

Some readers indicated that even direct downloads from the Catalog initially progressed but failed around the 60% mark, resulting in a failure to install.

Resolving Installation Issues

Accept TOS of windows 11 media creation tool

If you’re grappling with installation woes, consider utilizing the Media Creation Tool. This method not only installs KB5065426 but also addresses other potential system complications.

To initiate this process, download and install the Media Creation Tool from Microsoft’s official site. Choose “Upgrade this PC”, making sure the option to preserve personal files is selected. After Windows reinstalls, check for updates. In some cases, KB5065426 may already be set for download.

Should this tool fail to yield results or if you do not see the file preservation option, the Update Assistant Tool is a viable alternative.

Issues Beyond Installation

It’s worth noting that installation errors aren’t the only concerns users have reported. Instances of broken file sharing functionality have emerged across systems following the KB5065426 update. Users are experiencing issues with SMB/network shares, leading to persistent “System error 86” messages during connection attempts.

This disruption has notably affected small office environments, with multiple machines encountering connection failures post-update. Some individuals reported that they are unable to access any file shares post-installation, even attempting to roll back the update without success.

Uninstall Windows 11 September 2025 Update

For those experiencing connectivity issues, navigate to Settings > Windows Update > Update history > Uninstall updates to remove KB5065426. A warning about removing a security patch will appear, which can be bypassed if the update’s installation led to significant problems.

If removal isn’t possible due to timing limitations, using the Media Creation Tool to reinstall or perform an in-place upgrade should be considered, although it is important to acknowledge that this may exclude valuable security fixes and features such as Emoji 16 support.

I have also made inquiries with Microsoft about the numerous installation errors. Historically, it is not uncommon for server-side adjustments to be initiated to resolve widespread issues, and we anticipate potential changes in the near future.

Conclusion

Ensuring your system is up-to-date and functional is paramount, particularly as updates like these roll out. If you’re facing challenges with the installation of Windows 11 KB5065426, follow the suggestions outlined and remain proactive in addressing potential issues that arise.

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