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How to Fix Windows 11 Install Error 0x800f0991 (January 2026 Update)

Are you unable to install the January 2026 Security Update (KB5074109) due to error 0x800f0991? You are not alone. Since January 23, 2026, thousands of Windows 11 users have reported that their update progress reaches 90% and then fails with this specific code. This error indicates a "CBS XML Parser Failure," meaning your system cannot read the update's metadata. Here is the verified guide to fixing error 0x800f0991 right now.

​Why is Error 0x800f0991 Happening Today?

​Unlike common update bugs, the 0x800f0991 error is triggered by corrupted XML metadata within the local Component Based Servicing (CBS) engine. This prevents Windows from "handshaking" with the KB5074109 package. This issue is particularly affecting Windows 11 builds 24H2 and 25H2, and traditional troubleshooters often fail to detect the root cause.

​3 Steps to Fix Error 0x800f0991

​Follow these verified methods to force the update to install:

  1. ​Reset Windows Update Components via CMD: Open Command Prompt as Administrator and run these commands to clear the stuck metadata:
    • ​net stop wuauserv
    • ​net stop bits
    • ​rd /s /q %windir%\SoftwareDistribution
    • ​net start wuauserv
    • ​net start bits
  2. ​Repair the Component Store: In the same Admin Command Prompt, type: dism /online /cleanup-image /startcomponentcleanup This command is more effective than the standard "RestoreHealth" for this specific XML failure, as it prunes corrupted metadata versions.
  3. ​Manual SSU Installation: Many users in the Microsoft Community have found that installing the latest Servicing Stack Update (SSU) manually from the Microsoft Update Catalog before retrying the KB5074109 patch bypasses the 0x800f0991 block.

​Official Microsoft Recommendation

​Microsoft has confirmed that if the error persists, the corruption may reside in the system image itself. In such cases, a "Repair Install" (In-place Upgrade) using the official Windows 11 ISO is the only supported way to fix the servicing stack without losing your personal files.