CVE-2026-116686
mediumThe Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients.
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Affected products
Not reported by the source (unknown — not "none").
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
No vendor advisory or patch reference tagged by NVD. Check the references below.
References
- https://github.com/modelcontextprotocol/python-sdk/commit/5ebdfed4060d8e5b11b8e2348f86bad4... security-advisories@github.com
- https://github.com/modelcontextprotocol/python-sdk/commit/6705402e246dc4eb1fcdf4d9902b78d3... security-advisories@github.com
- https://github.com/modelcontextprotocol/python-sdk/pull/3394 security-advisories@github.com
- https://github.com/modelcontextprotocol/python-sdk/pull/3396 security-advisories@github.com
- https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0 security-advisories@github.com
- https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0 security-advisories@github.com
- https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-rwrf-2pqf-9j8j security-advisories@github.com