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kritisch

CVE-2026-32871

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

Veröffentlicht Geändert CWE 918
In der Trivy Database seit spätestens 24. Okt. 2026, 07:11 UTCWann der Eintrag vor diesem Build hinzukam, ist nicht erfasst.

Einstufung nach Quelle

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

Trivys eigenes Label ist CRITICAL. Kritisch laut NVD, GHSA. Niedriger laut Red Hat (hoch).

Beschreibung

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.

Betroffene Pakete und behobene Versionen

QuellePaketBehoben in
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-rhel9kein Fix angegeben

Referenzen

Alle 15 Referenzen

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.