SSRF in Modelcontextprotocol Python-Sdk
CVE-2026-116686
The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.10.0 until 1.30.0 and 2.2.0, ClientSession, ClientSessionGroup, and Client tool calls validate server-declared outputSchema documents with jsonschema's default resolver, causing an unresolved $ref value to fetch an HTTP, HTTPS, or file URL from the client's network and filesystem context. A server can trigger blind requests or local-file reads and can stall every session in the process because resolution runs synchronously on the event loop without a timeout. This issue is fixed in versions 1.30.0 and 2.2.0.
Vulnerability class: SSRF (Server-Side Request Forgery)
Published .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Modelcontextprotocol Python-Sdk — versions >= 1.10.0, < 1.30.0, >= 2.0.0, < 2.2.0
Weakness classification (CWE)
References
- github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-rwrf-2pqf-9…
- github.com/modelcontextprotocol/python-sdk/pull/3394
- github.com/modelcontextprotocol/python-sdk/pull/3396
- github.com/modelcontextprotocol/python-sdk/commit/5ebdfed4060d8e5b11b8e2348f86b…
- github.com/modelcontextprotocol/python-sdk/commit/6705402e246dc4eb1fcdf4d9902b7…
- github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0
- github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0
Frequently asked questions
- What is CVE-2026-116686?
- CVE-2026-116686 is a medium-severity vulnerability in Modelcontextprotocol Python-Sdk, classified under Server-Side Request Forgery (SSRF). CVSS score: 6.5/10. Published 2026-10-27.
- How severe is CVE-2026-116686?
- Medium severity. CVSS v3 base score is 6.5 out of 10.