### 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 `TransportSecuritySettings`, a malicious website could exploit DNS rebinding to bypass same-origin policy restrictions and send requests to the local MCP server. This could allow an attacker to invoke tools or access resources exposed by the MCP server on behalf of the user in those limited circumstances. Note …
GHSA-9h52-p55h-vw2f: Model Context Protocol (MCP) Python SDK does not enable DNS rebinding protection by default
The Model Context Protocol (MCP) Python SDK lacks default DNS rebinding protection for HTTP-based servers, enabling attacks to bypass same-origin policy and access local MCP servers.