MCP Python SDK: WebSocket server transport does not support Host/Origin validation
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.6epss 0.1%
exploitation probability
0.1%top 95% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Affected products
modelcontextprotocol · python-sdkReferences
https://github.com/modelcontextprotocol/python-sdk/commit/777b8d06710c140e3606b0d4598e2aa48546c266https://github.com/modelcontextprotocol/python-sdk/pull/2992https://github.com/modelcontextprotocol/python-sdk/releases/tag/v1.28.1https://github.com/modelcontextprotocol/python-sdk/security/advisories/GHSA-vj7q-gjh5-988w