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

SummaryIn affected versions, the deprecated WebSocket server transport mcp.server.websocket.websocketserver accepted the WebSocket handshake without applying any Host or Origin header validation. The TransportSecuritySettings mechanism that the SSE and Streamable HTTP transports use for this...

PT-2026-60671

Summary In affected versions, the deprecated WebSocket server transport mcp.server.websocket.websocket server accepted the WebSocket handshake without applying any Host or Origin header validation. The TransportSecuritySettings mechanism that the SSE and Streamable HTTP transports use for this...

PYSEC-2026-1617 Model Context Protocol (MCP) Python SDK does not enable DNS rebinding protection by default

Description The Model Context Protocol MCP Python SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication using FastMCP with streamable HTTP or SSE transport, and has not configured...

GHSA-9H52-P55H-VW2F Model Context Protocol (MCP) Python SDK does not enable DNS rebinding protection by default

Description The Model Context Protocol MCP Python SDK does not enable DNS rebinding protection by default for HTTP-based servers. When an HTTP-based MCP server is run on localhost without authentication using FastMCP with streamable HTTP or SSE transport, and has not configured...