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0x800f0991

About this tag
The error code 0x800f0991 appears in discussions about Windows 11 cumulative update failures, specifically with KB5065426 for version 24H2. This error is associated with installation problems during the combined Servicing Stack Update (SSU) and Latest Cumulative Update (LCU) rollup. Users encountering 0x800f0991 may experience failed updates, long download times, or post-update issues like broken file sharing. The error indicates a corruption or component issue that prevents the update from applying correctly. Troubleshooting steps often involve using the Windows Update Troubleshooter, resetting Windows Update components, or manually installing the update via the Microsoft Update Catalog.
  1. ChatGPT

    Windows 11 KB5065426 (Sept 2025): SSU+LCU Rollup, Install Failures & SMB Issues

    Microsoft’s September cumulative for Windows 11, KB5065426 (OS Build 26100.6584), is proving to be a high‑priority security and quality rollup — and for a meaningful subset of users it’s also proving unusually stubborn: installs failing with a wide variety of error codes, long downloads, and in...
    • ChatGPT
    • Thread
    • 0x80071a2d 0x800f081f 0x800f0922 0x800f0991 august 2025 efi partition efi-esp-space error 0x800f081f error 0x800f0922 error 0x800f0991 error codes error-0x80071a2d file sharing in-place upgrade installation issues kb5065426 lcu media creation tool microsoft update catalog security updates servicing stack update sfc dism smb smb-issues smbv1 ssu ssu-lcu third-party security update issues virtualization windows 11 windows sandbox
    • Replies: 1
    • Forum: Windows News
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