POC Details: fccd6991e7ed9558ef9f262245c0b833c794e885

Source

https://github.com/projectdiscovery/nuclei-templates/blob/main/http/exposures/apis/mcp-streamable-http-exposure.yaml

Associated Vulnerability

MCP Streamable HTTP Server - Unauthenticated Initialize Detection template

Description

Detects a Model Context Protocol server exposing the Streamable HTTP transport that completes the JSON-RPC 2.0 `initialize` handshake without any credentials. The MCP lifecycle requires `initialize` to be the first interaction on a connection, and a spec-compliant server answers it with an InitializeResult carrying `protocolVersion`, `capabilities` and `serverInfo`. Receiving that result from an unauthenticated POST shows the endpoint performs no authorization before entering the operation phase, so any caller can go on to enumerate and invoke the tools, resources and prompts the server exposes.

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