{"id":"CVE-2026-116685","state":"PUBLISHED","title":"Model Context Protocol Python SDK: HTTP client transports followed cross-origin redirects carrying custom headers and bodies","description":"The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.8.0 until 1.30.0 and 2.2.0, streamable_http_client, streamablehttp_client, sse_client, ClientSessionGroup, OAuth, and create_mcp_http_client client paths enable follow_redirects and follow redirects to a different origin, forwarding caller-supplied custom credential headers and, for 307 or 308 responses, the request body. An attacker who can influence a trusted endpoint's redirect destination can receive that material. This issue is fixed in versions 1.30.0 and 2.2.0.","publishedAt":"2026-10-27T19:26:46.926Z","updatedAt":"2026-10-30T15:03:50.436Z","severity":{"score":5.9,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["modelcontextprotocol python-sdk"],"affected":[{"vendor":"modelcontextprotocol","product":"python-sdk","versions":[{"version":">= 1.8.0, < 1.30.0","status":"affected"},{"version":">= 2.0.0, < 2.2.0","status":"affected"}]}],"references":["https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-5h93-6whr-6q8j","https://github.com/modelcontextprotocol/python-sdk/pull/3397","https://github.com/modelcontextprotocol/python-sdk/pull/3448","https://github.com/modelcontextprotocol/python-sdk/commit/2106335745563b2321b8c73fef2c12903d00aa6e","https://github.com/modelcontextprotocol/python-sdk/commit/c6762e821c527925f0b617db216d00fbd1d0bf99","https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0","https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0"],"weaknesses":["CWE-200"],"ingestedAt":"2026-10-30T15:18:06.520Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/116xxx/CVE-2026-116685.json","commit":"70fdf27998a84c5869ef58058ee273012c4794a3","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-116685","state":"PUBLISHED","datePublished":"2026-10-27T19:26:46.926Z","dateUpdated":"2026-10-30T15:03:50.436Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-10-26T20:00:59.830Z"},"containers":{"cna":{"title":"Model Context Protocol Python SDK: HTTP client transports followed cross-origin redirects carrying custom headers and bodies","descriptions":[{"lang":"en","value":"The Model Context Protocol Python SDK is the official Python SDK for Model Context Protocol servers and clients. From 1.8.0 until 1.30.0 and 2.2.0, streamable_http_client, streamablehttp_client, sse_client, ClientSessionGroup, OAuth, and create_mcp_http_client client paths enable follow_redirects and follow redirects to a different origin, forwarding caller-supplied custom credential headers and, for 307 or 308 responses, the request body. An attacker who can influence a trusted endpoint's redirect destination can receive that material. This issue is fixed in versions 1.30.0 and 2.2.0."}],"affected":[{"vendor":"modelcontextprotocol","product":"python-sdk","versions":[{"version":">= 1.8.0, < 1.30.0","status":"affected"},{"version":">= 2.0.0, < 2.2.0","status":"affected"}]}],"references":[{"url":"https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-5h93-6whr-6q8j","name":"https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-5h93-6whr-6q8j","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/pull/3397","name":"https://github.com/modelcontextprotocol/python-sdk/pull/3397","tags":["x_refsource_MISC"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/pull/3448","name":"https://github.com/modelcontextprotocol/python-sdk/pull/3448","tags":["x_refsource_MISC"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/commit/2106335745563b2321b8c73fef2c12903d00aa6e","name":"https://github.com/modelcontextprotocol/python-sdk/commit/2106335745563b2321b8c73fef2c12903d00aa6e","tags":["x_refsource_MISC"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/commit/c6762e821c527925f0b617db216d00fbd1d0bf99","name":"https://github.com/modelcontextprotocol/python-sdk/commit/c6762e821c527925f0b617db216d00fbd1d0bf99","tags":["x_refsource_MISC"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0","name":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.30.0","tags":["x_refsource_MISC"]},{"url":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0","name":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.2.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":5.9,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-200","lang":"en","description":"CWE-200: Exposure of Sensitive Information to an Unauthorized Actor","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-10-27T19:26:46.926Z"},"source":{"advisory":"GHSA-5h93-6whr-6q8j","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-30T15:03:41.785776Z","id":"CVE-2026-116685","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-30T15:03:50.436Z"}}]}}}