Is there a public exploit for CVE-2026-32871?

No public exploit for CVE-2026-32871 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-32871?

CVE-2026-32871 scores CVSS 10 (v4.0), rated critical. EPSS puts the chance of exploitation in the next 30 days at 0.93%.

What does CVE-2026-32871 affect?

CVE-2026-32871 affects prefecthq fastmcp. It is part of the AI and agent stack (Model Context Protocol).

10.0 Critical

FastMCP is a Pythonic way to build MCP servers and clients.

CVE-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 buildurl() method. When an OpenAPI operation defines path parameters (e.g., /api/v1/users/{userid}), 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.

Part of the AI stack

This affects Model Context Protocol, in MCP & tool servers.

Assessment

CVSS: 10 (v4.0)
Severity: Critical
EPSS: 0.93% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 2 April 2026
Last updated: 26 October 2026
Affected: prefecthq · fastmcp
Weakness: CWE-918
Assigner: security-advisories@github.com

CVSS vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

At the source

References

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