How to Fix Fix Error 0x80070643 — Windows Update or .NET Install Failed on Windows
Getting error 0x80070643 during Windows Update, .NET Framework installation, or security update? Fix this common installation failure error.
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Main Troubleshooting Guide
How to Fix Windows Update Errors →Complete symptoms, causes, and step-by-step solutions
Symptoms
You might be experiencing this problem if you notice:
- •Windows Update fails with error 0x80070643
- •.NET Framework update keeps failing with this error
- •Security Intelligence Update for Defender fails with 0x80070643
- •KB update downloads but fails at installation step
- •Error appears repeatedly in Windows Update history
- •Cumulative update partially installs then rolls back with this error
Common Causes
- ⚠Corrupted .NET Framework installation
- ⚠Windows Defender definition update conflict
- ⚠Windows Installer service not running properly
- ⚠Corrupted Windows Update components
- ⚠Previous failed update left partial installation
- ⚠Third-party antivirus interfering with update installation
Solutions
Solution 1: Fix .NET Framework
- 1Most common cause of 0x80070643 is .NET corruption:
- 2Download Microsoft .NET Framework Repair Tool from microsoft.com
- 3Run the repair tool — it fixes most .NET issues automatically
- 4Alternative manual fix:
- 5Settings → Apps → Optional features → More Windows features
- 6Uncheck ".NET Framework 3.5" and ".NET Framework 4.8"
- 7Click OK → restart → re-check both → OK → restart
- 8Try the Windows Update again
Solution 2: Fix Defender Update Failure
- 1If the failing update is "Security Intelligence Update for Defender":
- 2Open Windows Security → Virus & threat protection
- 3Click "Protection updates" → "Check for updates"
- 4This forces a direct Defender update outside Windows Update
- 5Alternative: CMD as Admin:
- 6"C:\Program Files\Windows Defender\MpCmdRun.exe" -SignatureUpdate
- 7If still failing: delete old definitions and re-download:
- 8"C:\Program Files\Windows Defender\MpCmdRun.exe" -RemoveDefinitions -All
Solution 3: Reset Windows Update Components
- 1CMD as Admin — run these commands in order:
- 2net stop wuauserv
- 3net stop cryptSvc
- 4net stop bits
- 5net stop msiserver
- 6ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
- 7ren C:\Windows\System32\catroot2 catroot2.old
- 8net start wuauserv
- 9net start cryptSvc
- 10net start bits
- 11net start msiserver
- 12Try the update again
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