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KB5079473 on build 26200.8037 fails to install - error code 0x800f0991

Rob 0 Reputation points
2026-03-12T19:33:53.7866667+00:00

It downloads then attempts to install the abovementioned update. The installation stops and returns the error code given above. I have tried about ten times.

I have tried the troubleshooter (which says there are no issues), run a few DISM commands and an SFC. I am not running a third party virus checker. I have tried to download the update and run it manually but this also fails in the same way.

This is a newly built (last week) PC from a reputable company and I am running Win 11 Pro.

I have a CBS log if needed.

Is this a Microsoft issue that will be fixed? What else do I need to do to get this update?

Windows for home | Windows 11 | Windows update
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  1. Q&A Assist
    2026-03-12T19:34:10.1666667+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    For KB5079473 (build 26200.8037) failing with 0x800f0991 on a new Windows 11 Pro PC, this behavior can be a transient Microsoft-side issue with the update itself. In the referenced case, after multiple failures and trying DISM, SFC, the troubleshooter, and manual installation, the update eventually installed successfully without any additional action once Microsoft corrected the underlying problem.

    Given that DISM, SFC, and the Windows Update troubleshooter have already been run and the system is otherwise healthy, the next step is to wait and retry periodically. Allow Windows Update to attempt installation again over the next day or two; if it is the same issue, it should self-correct and install successfully once the backend or package issue is resolved.

    If the update continues to fail over time, monitor Windows Update for any newer cumulative updates that supersede KB5079473 and install those instead, as they typically include the same fixes and may bypass the specific failure affecting this build.

    References:

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  1. Rob 0 Reputation points
    2026-03-12T19:37:30.8866667+00:00

    How long should I wait for a fix?

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