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    2 vulnerabilities found for fastmcp by PrefectHQ

    CVE-2026-32871 (GCVE-0-2026-32871)

    Vulnerability from nvd – Published: 2026-04-02 14:52 – Updated: 2026-06-30 12:07
    VLAI
    Title
    FastMCP OpenAPI Provider has an SSRF & Path Traversal Vulnerability
    Summary
    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.
    Severity
    10 (Critical)
    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
    8.5 (High)
    CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
    SSVC
    Exploitation: poc Automatable: yes Technical Impact: total
    CISA Coordinator (v2.0.3)
    CWE
    • CWE-918 - Server-Side Request Forgery (SSRF)
    Assigner
    References
    Impacted products
    Show details on NVD website
    To clipboard 

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    CVE-2026-32871 (GCVE-0-2026-32871)

    Vulnerability from cvelistv5 – Published: 2026-04-02 14:52 – Updated: 2026-06-30 12:07
    VLAI
    Title
    FastMCP OpenAPI Provider has an SSRF & Path Traversal Vulnerability
    Summary
    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.
    Severity
    10 (Critical)
    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
    8.5 (High)
    CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
    SSVC
    Exploitation: poc Automatable: yes Technical Impact: total
    CISA Coordinator (v2.0.3)
    CWE
    • CWE-918 - Server-Side Request Forgery (SSRF)
    Assigner
    References
    Impacted products
    Show details on NVD website
    To clipboard 

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