Malicious MCP Servers Can Split Instructions to Make AI Coding Agents Exfiltrate Secrets
A malicious tool server connected to an AI coding assistant can quietly walk off with SSH keys, environment secrets, source code, and customer data without ever sending one obviously harmful instruction. The trick can work even after a blunt version of the same theft is refused: split the request into fragments that each look routine, place them in channels the assistant already uses, and let the agent stitch them together and send the data back. The attack targets coding tools that connect to outside servers over the Model Context Protocol (MCP), the open standard that lets AI assistants call external tools. A malicious MCP server can put one fragment in a tool description and another in a tool result; some setups also support server-initiated sampling. MCP does preserve structured tool and result boundaries. But ASSET Research Group's tests show agents can still combine instructions across them in the same working context, so no single fragment has to contain the whole mal...
î ‚Aug 11, 2026