NuGet Gallery: Arbitrary Blob Overwrite via Nuspec Confusion and URI Fragment Truncation

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Summary

CVECVE-2026-39399
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-14 23:16:29 UTC
Updated2026-04-17 15:38:09 UTC
DescriptionNuGet 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.

Risk And Classification

Primary CVSS: v3.1 9.6 CRITICAL from [email protected]

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

EPSS: 0.002640000 probability, percentile 0.499470000 (date 2026-04-17)

Problem Types: CWE-20 | CWE-22 | CWE-20 CWE-20: Improper Input Validation | CWE-22 CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.6CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H
3.1CNADECLARED9.6CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA NuGet NuGetGallery affected < 0e80f87628349207cdcaf55358491f8a6f1ca276 Not specified

References

ReferenceSourceLinkTags
github.com/NuGet/NuGetGallery/commit/0e80f87628349207cdcaf55358491f8a6f1... [email protected] github.com
github.com/NuGet/NuGetGallery/security/advisories/GHSA-9r3h-v4hx-rhfr [email protected] github.com
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