Is this vulnerability remotely exploitable?

Yes. An attacker can exploit this issue remotely by submitting a crafted NuGet package containing a malicious .nuspec file to a vulnerable NuGet Gallery instance. The backend job processes the package and triggers the vulnerability without requiring local access.

What level of access does an attacker need?

The attacker typically needs the ability to publish or upload packages to the affected gallery. No direct access to the storage backend is required; the backend job's elevated storage privileges are abused indirectly through crafted metadata.

What is the safest general fix pattern for developers?

The safest pattern is to treat all .nuspec metadata as untrusted, apply strict validation and normalization, and ensure that storage paths or blob keys are derived from canonical, server-controlled representations. Avoid constructing URIs or paths directly from raw user input, and enforce that any derived path is constrained to an expected namespace.

Severity:

CRITICAL RISK

(9.6)

Improper Input Validation and Path Manipulation (CWE-20/CWE-22) in NuGet Gallery Backend .nuspec Handling

CVE-2026-39399

Published:

Apr 14, 2026

Status:

Awaiting Analysis

Summary

Affected Context

Exploit Preconditions

Why This Happens

Potential Impact

General Mitigation Guidance

How Teams Detect Issues Like This

Frequently Asked Questions

Source

NDV

Recent Vulnerabilities

CWE-74;CWE-89

HIGH RISK

HIGH

(7.3)

SQL Injection via Unsanitized ID Parameter (CWE-89) in Pharmacy Sales and Inventory System /ajax.php

Database Compromise and Data Integrity Loss

April 27, 2026

CWE-863

HIGH RISK

HIGH

(8.5)

Incorrect Authorization (CWE-863) in OpenClaw chat.send Session Management

Privilege Escalation and Unauthorized Session Control

April 27, 2026

Vulnerability Type

Category:

Improper Input Validation and Path Traversal

CWE:

CWE-20;CWE-22

Impact:

Remote Code Execution and Arbitrary File/Blob Write

Severity:

CRITICAL RISK

(9.6)

CVSS Version:

3.1

Vulnerability Type

Category:

Improper Input Validation and Path Traversal

CWE:

CWE-20;CWE-22

Impact:

Remote Code Execution and Arbitrary File/Blob Write

Severity:

CRITICAL RISK

(9.6)

CVSS Version:

3.1

Catch This CVE While Code Is Being Written

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Improper Input Validation and Path Manipulation (CWE-20/CWE-22) in NuGet Gallery Backend .nuspec Handling

Summary

Affected Context

Exploit Preconditions

Why This Happens

Potential Impact

General Mitigation Guidance

How Teams Detect Issues Like This

Frequently Asked Questions

Source

Recent Vulnerabilities

HIGH RISK

HIGH

(7.3)

SQL Injection via Unsanitized ID Parameter (CWE-89) in Pharmacy Sales and Inventory System /ajax.php

HIGH RISK

HIGH

(8.5)

Incorrect Authorization (CWE-863) in OpenClaw chat.send Session Management

Vulnerability Type

Vulnerability Type

Vulnerability Type

Catch This CVE While Code Is Being Written

Ship clean & secure code faster

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