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CVE-2026-39399

9.6 · CRITICAL

NuGet Gallery is a package repository that powers nuget.org.

Published Apr 14, 2026CWE-20EPSS 0.82%

Overview

CVE-2026-39399 is a critical-severity vulnerability. It was published on April 14, 2026 and has a CVSS 3.1 base score of 9.6 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.6, rated CRITICAL. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/NuGet/NuGetGallery/commit/0e80f87628349207cdcaf55358491f8a6f1ca276GitHubgithub.com/NuGet/NuGetGallery/security/advisories/GHSA-9r3h-v4hx-rhfr

How CyberStrike helps

Frequently asked questions

What is CVE-2026-39399?

CVE-2026-39399 is a critical-severity vulnerability. It was published on April 14, 2026 and has a CVSS 3.1 base score of 9.6 (CRITICAL).

How severe is CVE-2026-39399?

This vulnerability has a CVSS 3.1 base score of 9.6, rated CRITICAL. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-39399?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-39399?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-39399 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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