CVE-2026-39399: Nuget Nugetgallery

Critical severity, CVSS 9.6. EPSS: 0.8% chance of exploitation in the next 30 days.

NuGet Gallery is a package repository that powers nuget.org. A security vulnerability exists in the NuGetGallery backend job’s handling of .nuspec files within NuGet packages. An attacker can supply a crafted nuspec file with malicious metadata, leading to cross package metadata injection that may result in remote code execution (RCE) and/or arbitrary blob writes due to insufficient input validation. The issue is exploitable via URI fragment injection using unsanitized package identifiers, allowing an attacker to control the resolved blob path. This enables writes to arbitrary blobs within the storage container, not limited to .nupkg files, resulting in potential tampering of existing content. This issue has been patched in commit 0e80f87628349207cdcaf55358491f8a6f1ca276.

Affected products

• Nuget Nugetgallery: before 0e80f87628349207cdcaf55358491f8a6f1ca276 (fixed in 0e80f87628349207cdcaf55358491f8a6f1ca276)

Published 2026-04-14. Last modified 2026-07-24.