What happened
OX Security uncovered an architectural flaw in the Model Context Protocol that enables arbitrary command execution on systems running vulnerable MCP implementations. The flaw is *systemic*, not implementation-specific, and is reachable via prompt injection plus standard MCP message flow.
Scale
- 150M+ downloads of vulnerable MCP libraries.
- 7,000+ publicly accessible servers.
- Up to 200,000 vulnerable instances total.
Cursor, VS Code, Windsurf, Claude Code, and Gemini-CLI are all reachable via this class of issue.