GHSA-vv7q-7jx5-f767: fastmcp (CVE-2026-32871)

Package	Ecosystem	Affected	Fixed in
fastmcp	PyPI	<3.2.0	3.2.0

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

FastMCP's OpenAPI Provider, in the fastmcp PyPI package before version 3.2.0, does not URL-encode path parameter values when building backend request URLs, so path traversal sequences can escape the intended API prefix. An attacker who can send requests through an MCP client can reach arbitrary backend endpoints, and those requests carry the provider's configured authorization headers, which the source describes as authenticated SSRF. The fix is to upgrade to fastmcp 3.2.0 or later, and the source also recommends URL-encoding path parameter values before substitution.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
10.0	Critical	4.0	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	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0092, the 61st percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:07 UTC First seen by agentprime
31 Oct 2026, 14:07 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.