Components Vulnerabilities Pricing MCP API

fastmcp 2.13.0rc3 | Vulnerabilities | Sonatype Guide

fastmcp

2.13.0rc3

fastmcp 2.13.0rc3

PublishedOct 24, 2025•Policy

compliance

Developer Trust Score

N/A

Recommended Version:x.y.z

Latest version with 0 known vulnerabilities that meets your policy.

Compare Versions

Severity

Critical (1)

High (0)

Medium (0)

Low (0)

CVSS Score

0.010.0

EPSS Score

0.01.0

Malware

KEV StatusPublished

10.0CVE-2026-32871

FastMCP is a Pythonic way to build MCP servers and clients. Prior to version 3.2.0, the OpenAPIProvider in FastMCP exposes internal APIs to MCP clients by parsing OpenAPI specifications. The RequestDirector class is responsible for constructing HTTP requests to the backend service. A vulnerability exists in the _build_url() method. When an OpenAPI operation defines path parameters (e.g., /api/v1/users/{user_id}), the system directly substitutes parameter values into the URL template string without URL-encoding. Subsequently, urllib.parse.urljoin() resolves the final URL. Since urljoin() interprets ../ sequences as directory traversal, an attacker controlling a path parameter can perform path traversal attacks to escape the intended API prefix and access arbitrary backend endpoints. This results in authenticated SSRF, as requests are sent with the authorization headers configured in the MCP provider. This issue has been patched in version 3.2.0.

SeverityCritical

PublishedApr 1, 2026