{"id":"CVE-2026-116686","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-116686","generatedAt":"2026-10-28T01:11:40.491Z","title":"The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients.","description":"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.","published":"2026-10-27T20:17:14.000Z","lastModified":"2026-10-27T20:17:14.000Z","status":"Received","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H"},"cwe":["CWE-918"],"affected":[],"epss":null,"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and no EPSS score yet. Track it; it rarely justifies an emergency change on its own."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-27T20:17:14.000Z","detail":{"score":"6.5","severity":"MEDIUM","publishedAt":"2026-10-27T20:17:13.740Z"},"summary":"New CVE, medium severity (CVSS 6.5)."}],"references":[{"url":"https://github.com/modelcontextprotocol/python-sdk/commit/5ebdfed4060d8e5b11b8e2348f86bad4d1fb8836","source":"security-advisories@github.com"},{"url":"https://github.com/modelcontextprotocol/python-sdk/commit/6705402e246dc4eb1fcdf4d9902b78d3c9c36e1b","source":"security-advisories@github.com"},{"url":"https://github.com/modelcontextprotocol/python-sdk/pull/3394","source":"security-advisories@github.com"},{"url":"https://github.com/modelcontextprotocol/python-sdk/pull/3396","source":"security-advisories@github.com"},{"url":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0","source":"security-advisories@github.com"},{"url":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0","source":"security-advisories@github.com"},{"url":"https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-rwrf-2pqf-9j8j","source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-116686","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}