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Vulnerability record · CVE-2026-39399 · published 14 April 2026

CVE-2026-39399: Improper input validation vulnerability

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.

9.6 CVSS 3.1 Critical EPSS 0.82% · top 44.5% CWE-20 · Improper input validationCWE-22 · Path traversal Awaiting Analysis
9.6CVSS 3.1 base score
0.82%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
24 Jul 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

References

LinkTags
https://github.com/NuGet/NuGetGallery/commit/0e80f87628349207cdcaf55358491f8a6f1ca276
https://github.com/NuGet/NuGetGallery/security/advisories/GHSA-9r3h-v4hx-rhfr

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Source: NIST National Vulnerability Database (record CVE-2026-39399), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.