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Vulnerabilidades / CVE-2026-32871

crítica

CVE-2026-32871

fastmcp: FastMCP: Authenticated Server-Side Request Forgery via path traversal in OpenAPI path parameters

Publicada Modificada CWE 918
En la Trivy database desde, como mínimo, el 24 oct 2026, 07:11 UTCNo consta cuándo entró antes de ese build.

Severidad por fuente

NVD10.0CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
GHSA10.0CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
Red Hat8.5CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

La etiqueta propia de Trivy es CRITICAL. Crítica según NVD, GHSA. Más baja según Red Hat (alta).

Descripción

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.

Paquetes afectados y versiones corregidas

FuentePaqueteCorregido en
pip::GitHub Security Advisory pipfastmcp3.2.0
chainguardmcp-atlassian0.23.0-r0
echo pip::Echo OSVfastmcp2.14.5+echo.1
Red Hatsatellite/foreman-mcp-server-rhel9sin corrección indicada

Referencias

Las 15 referencias

Vulnerability data compiled from the Trivy vulnerability database (trivy-db, Aqua Security, Apache License 2.0), which aggregates third-party advisories. CVE records are published by The MITRE Corporation under the CVE Terms of Use; CVE is a trademark of MITRE. This product uses data from the NVD API but is not endorsed or certified by the NVD. Severity, titles and advisory data from the GitHub Advisory Database (CC BY 4.0), Red Hat security data (CC BY 4.0) and the other sources linked on each entry. Entries may be summarised or re-formatted; the linked original is the authoritative record.