CVE-2026-86439

Received Received - Intake

Path Traversal Vulnerability in MCP Tool Before 0.30.0

Publication date: 2026-09-07

Last updated on: 2026-09-07

Assigner: VulnCheck

Description

knowns versions before 0.30.0 fail to validate filesystem paths in MCP tool arguments, allowing attackers to read, create, overwrite and delete files outside the project directory. Attackers can supply path arguments containing directory traversal sequences to access arbitrary Markdown files accessible to the server process.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-09-07

Last Modified

2026-09-07

Generated

2026-09-08

AI Q&A

2026-09-08

EPSS Evaluated

N/A

NVD

CVE-2026-86439

EUVD

EUVD-2026-72555

Affected Vendors & Products

Currently, no data is known.

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-22	The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Attack-Flow Graph

Executive Summary

This vulnerability affects versions before 0.30.0 of a software that fails to validate filesystem paths in MCP tool arguments. Attackers can use directory traversal sequences in path arguments to read, create, overwrite, or delete files outside the intended project directory. This includes accessing arbitrary Markdown files accessible to the server process.

Detection Guidance

To detect this vulnerability, inspect MCP tool arguments for path inputs containing directory traversal sequences like '../' or absolute paths. Check server logs for unusual file access patterns outside the project directory. Validate if the MCP server version is below 0.30.0.

Impact Analysis

An attacker could exploit this to access sensitive files, modify or delete critical data, or plant malicious files on the server. This could lead to data breaches, system compromise, or unauthorized access to confidential information.

Compliance Impact

This vulnerability could lead to unauthorized access or exposure of sensitive data, violating GDPR's data protection requirements and HIPAA's safeguards for protected health information. Non-compliance may result in legal penalties, fines, or reputational damage.

Mitigation Strategies

Immediately upgrade the MCP server to version 0.30.0 or later. Implement strict input validation for all file path arguments in MCP tools. Restrict server process permissions to limit file system access. Monitor for unauthorized file operations.

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