Windows failed to install the following update with error 0x80070643

Several users of Windows 10 are reporting that Windows Defender updates are failing to install and they receive a message:

Windows failed to install the following update with error 0x80070643

Windows Defender is failing to install updates

One user reported that the issue started for him after Cumulative Update for Windows 10 Version 1703 for x64-based Systems (KB4016250) was installed.

Another aggrieved user said:

This problem is not just limited to Insider builds I should add. I have checked several computers and the error occurs even on version 1607, which is the version on consumer computers! How many non tech users are now being left vulnerable because of this mess up. Also how many will do manual updates?

@PaulStreeting tweeted to us:

I have tested this bug on v1607 and does not apply only to ‘Insiders’ but the one pushed to users now..what is worrying is that the problem happens on v1607…so how many users are doing the manual update? Even after that it shows as error.

Microsoft has confirmed that they are aware of this issue and will roll out a fix soon:

Thank you for your patience regarding Windows Defender update error 0x80070643. We are aware of the issue and trying to roll out a mitigation as soon as possible. Meanwhile, to get your machine back to a protected state, you can manually download and apply the latest Definition Update.

windows defender updates failing

Check if your Windows Defender is updating automatically

I strongly urge you to check if your Windows Defender is updating automatically. If not, you should download and install the Windows Defender updates manually.

Open Windows Defender > Update > Update definitions. Or else, go to Settings > Update & Security > Windows Update > Check for updates. See if you can update it automatically.

If you cannot and if you are facing this issue, it is recommended that you update Windows Defender manually periodically till the problem is fixed by Microsoft.

Update Windows Defender manually in Windows

If you don’t want to get into the mess of checking up for updates, downloading them and applying them, I suggest that you use a third-party freeware antivirus software till Microsoft fixes the issue.

If you wish to troubleshoot the issue futher, perhaps this post will help you – Windows Defender will not update definitions.

Posted by on , in Category Security with Tags
Anand Khanse is the Admin of, a 10-year Microsoft MVP Awardee in Windows (2006-16) & a Windows Insider MVP. Please read the entire post & the comments first, create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers while installing freeware.


  1. NahNood

    Nothing new, it always does this for short times eventually. lol

  2. The real Yoda SAN ™

    I manually updated latest defender definitions using update mini tool and no pb .
    That said I ‘m still using build 14393.222 and stopped windows updates for now . :p

  3. Paul Streeting

    Not great though when you don’t know if it is actually working right or not though. This time it seems a more serious issue.

  4. Paul Streeting

    Just seems that every update Microsoft makes to Windows 10 it brings in more bugs than ever. Check in the reliability monitor to see though if it is listed as a ‘failed update’ or not as mentioned in the article.
    I did a manual update and it shows as a failed update which is why I am left wondering if the AV is up to date or not.

  5. LightInTheNight

    If I use the Windows 10 update manager i get the error messeage,
    but if I open Windows Defeneder and go to the update there, everythings work fine .
    Not the hardest workaround:)

  6. Paul Streeting

    Check in the ‘reliability monitor’ as I did when the problem started. It shows ‘failed updates’. At the time of writing this 5th April it seems that Microsoft has at least now sorted the problem very quickly. I wonder why…. Is it user power winning?

  7. Brian Wescombe

    I thought last Friday this was something I’d done (upgraded to 1703 build and was reconfiguring some things). Although it’s a problem I’m glad I’m not alone. Still doing it this morning

  8. Brian Wescombe

    Still getting the error in the reliability monitor with a manual update

  9. Paul Streeting

    If Windows 10 was a car we’d have taken it back for a refund ages ago. Microsoft at the moment are saying Windows Defender is the best thing in it for a secure PC. However when we know it isn’t quite as good it’s worrying as a lot of non-tech users need it to be reliable. I just wish Microsoft would be more honest when there are problems and let users know about it via social media, etc. I am advising older people I help to grasp the basics of computing to use Avast or AVG free versions now on their computers.

  10. Paul Streeting

    Are you 100% sure it is updating and the error message isn’t telling the truth that the update failed? The error message seems to happen just after Defender says it has updated and not before…

  11. Paul Streeting

    That’s the part that concerned me when I found the problem. Had it actually updated Defender or not…

  12. Brian Wescombe

    Slightly concerning to say the least. I was getting error with Windows update, manual update and using the “%PROGRAMFILES%Windows DefenderMPCMDRUN.exe” -SignatureUpdate as well

  13. Brian Wescombe

    I use Avast but with the Defender periodic scanning active

  14. LightInTheNight

    Yes and now The windows 10 update manager work`s 100%
    Defender verson 1.239.867

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