ERROR CODE NU 1900

Question

How do I resolve the issue below effectively:

Error occurred while getting package vulnerability data: Unable to load the service index for source https://api.nuget.org/v3/index.json.

Answer 1

NU1900 indicates NuGet could not download vulnerability data from a package source. In this case, the source is https://api.nuget.org/v3/index.json.

To resolve it effectively:

1. Check network connectivity to nuget.org
   • Ensure the machine can reach api.nuget.org over HTTPS (no proxy, firewall, or DNS issues blocking it).
   • If there was a transient network problem (timeout, DNS error, etc.), retry restore after a few minutes.
2. Verify the source configuration
   • Open the NuGet configuration (NuGet.Config) and confirm that https://api.nuget.org/v3/index.json is correctly configured as a package source.
   • Make sure there are no typos or invalid URLs.
3. Clear NuGet HTTP cache
   • If the error is related to invalid or corrupted data, clear the HTTP cache and try again:

          dotnet nuget locals http-cache --clear
     

   • Then rerun restore so NuGet can re-download the vulnerability data.
4. If the problem persists
   • The issue is likely with the package source itself (for example, returning invalid JSON or being temporarily unavailable).
   • Contact the administrators of the package source (for nuget.org, check service status or organization network policies) to confirm there is no ongoing outage or filtering.

This warning does not necessarily block restore unless warnings are treated as errors; it indicates that vulnerability auditing could not be completed for that source.

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References:

• NuGet Warning NU1900