# Model Context Protocol Python SDK: Client fetched server-chosen $ref URLs while validating tool results against output schemas

Advisory record · `GHSA-rwrf-2pqf-9j8j`

- **Identifiers:** `GHSA-rwrf-2pqf-9j8j` · `CVE-2026-116686`
- **State:** Confirmed
- **Severity:** CVSS 6.5 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-918](https://cwe.mitre.org/data/definitions/918.html)
- **Tags:** [Server-side request forgery (SSRF)](https://agentprime.io/advisories/tag/ssrf.md)
- **Published:** 27 Oct 2026
- **Updated:** 27 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 27 Oct 2026, 21:05 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `mcp` (PyPI): affected `>=2.0.0, <2.2.0 || >=1.10.0, <1.30.0`; fixed in `2.2.0`, `1.30.0`

## 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

- 6.5 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0034, the 27th percentile, on 5 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](https://osv.dev/vulnerability/GHSA-rwrf-2pqf-9j8j)

## Sources

- [GitHub Advisory Database: GHSA-rwrf-2pqf-9j8j](https://github.com/advisories/GHSA-rwrf-2pqf-9j8j)
- [OSV: GHSA-rwrf-2pqf-9j8j](https://osv.dev/vulnerability/GHSA-rwrf-2pqf-9j8j)
- <https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-rwrf-2pqf-9j8j>
- <https://github.com/modelcontextprotocol/python-sdk/pull/3394>
- <https://github.com/modelcontextprotocol/python-sdk/pull/3396>
- <https://github.com/modelcontextprotocol/python-sdk/commit/5ebdfed4060d8e5b11b8e2348f86bad4d1fb8836>
- <https://github.com/modelcontextprotocol/python-sdk/commit/6705402e246dc4eb1fcdf4d9902b78d3c9c36e1b>
- <https://github.com/modelcontextprotocol/python-sdk>
- <https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0>
- <https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0>

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.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-rwrf-2pqf-9j8j>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-rwrf-2pqf-9j8j/>. Everything for agents: <https://agentprime.io/llms.txt>.