CVE-2026-59950

HIGH8.1

MCP Python SDK: WebSocket server transport does not support Host/Origin validation

Published Jul 15, 2026

Modified 2 weeks ago

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.

References

WEB

https://github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266

WEB

https://github.com/modelcontextprotocol/python-sdk/pull/2992

WEB

https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.28.1

WEB

https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-vj7q-gjh5-988w

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-59950

CVSS Analysis