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How to Fix Windows Update Error 0x80070643 (January 2026 Bug)

​Is your PC failing to install the latest security updates with error code 0x80070643 today? Since the January 2026 patch cycle, thousands of Windows 10 and 11 users are reporting that the KB5034441 (or the latest cumulative update) keeps failing. This frustrating bug is usually tied to a lack of space in your Recovery Partition. Here is the step-by-step guide to fixing the 0x80070643 error immediately.

​What is Error 0x80070643?

​This error code, specifically ERROR_INSTALL_FAILURE, most commonly occurs when the Windows Recovery Environment (WinRE) partition doesn't have enough free space to process the update's security patches (such as the BitLocker vulnerability fix). Even in 2026, many systems still default to a small recovery partition that blocks the newest patches.

​The Verified Fix: Resizing Your Partition (CMD Guide)

​Follow these steps carefully to resolve the error. Warning: This involves disk management; ensure your data is backed up.

  1. ​Open Command Prompt (Admin): Search for cmd, right-click, and select Run as Administrator.
  2. ​Check WinRE Status: Type reagentc /info and press Enter. If it's enabled, type reagentc /disable to prepare for the resize.
  3. ​Run Diskpart: Type diskpart.
    • ​Type list disk and then sel disk <your disk number> (usually 0).
    • ​Type list part and identify your OS partition (the big one) and the Recovery partition.
    • ​Select your OS partition: sel part <OS index>.
    • ​Shrink it by 250MB: shrink desired=250 minimum=250.
    • ​Select and delete your old Recovery partition: sel part <Recovery index> then delete partition override.
  4. ​Create a New Partition:
    • ​If your disk is GPT, type: create partition primary id=de94bba4-06d1-4d40-a16a-bfd50179d6ac then gpt attributes=0x8000000000000001.
    • ​Type format quick fs=ntfs label="Windows RE tools".
  5. ​Re-enable WinRE: Type exit, then in the main CMD window, type reagentc /enable.

​Why You Shouldn't Ignore This Error

​This update fixes a critical BitLocker security flaw (CVE-2024-20666). If your update fails with 0x80070643, your device remains vulnerable to physical security breaches. After following the resize steps, go back to Settings > Windows Update and click Retry. It should now install successfully!