中文

// CVE · PUBLISHED 2026-04-02

CVE-2026-32871

PrefectHQ / fastmcp · Red Hat / Red Hat Satellite 6.18 · Red Hat / Red Hat OpenShift AI (RHOAI)

10.0 · CVSS 4.0Critical

Description

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.

References

Related CVEs

← CVE Index: search every CVE from the last 30 days

This product uses the NVD API but is not endorsed or certified by the NVD. CVSS scores do not establish exploitation.