{"id":"CVE-2026-59950","aliases":["GHSA-vj7q-gjh5-988w","PYSEC-2026-3483"],"url":"https://o3.security/vulnerability/CVE-2026-59950","summary":"MCP Python SDK: WebSocket server transport does not support Host/Origin validation","details":"The MCP Python SDK, called mcp on PyPI, is a Python implementation of the Model Context Protocol (MCP). Prior to 1.28.1, the deprecated mcp.server.websocket.websocket_server transport accepted WebSocket handshakes without applying Host or Origin header validation, leaving no SDK-level way to restrict which origins could connect to applications that exposed that transport. This issue is fixed in version 1.28.1.","published":"2026-07-15T20:08:54.095Z","modified":"2026-08-12T03:51:23.887724251Z","cvss":null,"epss":{"score":0.00149,"percentile":0.04625,"asOf":"2026-08-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"mcp","fixedVersion":"1.28.1"}],"fix":{"url":"https://github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266","label":"modelcontextprotocol/python-sdk@777b8d0"},"references":[{"type":"WEB","url":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.28.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59950.json"},{"type":"ADVISORY","url":"https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-vj7q-gjh5-988w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59950"},{"type":"FIX","url":"https://github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266"},{"type":"FIX","url":"https://github.com/modelcontextprotocol/python-sdk/pull/2992"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:23.887724251Z"}}