Executive brief
mcp-debugger is a tool used for debugging Model Context Protocol (MCP) implementations. A security vulnerability in this tool allows an attacker to read sensitive files from the host system where the debugger is running. This could lead to the exposure of source code, configuration files, or other private data, potentially compromising the security of the development environment.
Technical details
A path traversal vulnerability exists in the `handleGetSourceContext` function within `src/server.ts` of mcp-debugger up to version 0.20.0. The vulnerability stems from improper validation of the `args.file` parameter, which is passed to `resolvePathForRuntime`. In 'host mode', this function returns the input path unchanged without enforcing workspace boundaries. Consequently, the path reaches direct filesystem operations such as `readFile`, `stat`, and `pathExists` in `src/implementations/file-system-impl.ts`. A remote attacker with low privileges can exploit this to perform arbitrary file reads on the host system. As of the advisory date, the vendor has not responded to disclosure attempts.
Affected products
- debugmcp mcp-debugger up to 0.20.0
Timeline
- 2026-04-26: disclosed: Initial public issue report on GitHub
- 2026-05-25: advisory: VulDB and NVD publication