All You Need Is MCP – LLMs Solving a DEF Con CTF Finals Challenge (wilgibbs.com)

At DEF CON 31’s legendary Capture The Flag (CTF) Finals, a milestone was reached as a complex challenge called “ico” was largely solved using large language models (LLMs) with minimal human intervention—marking the first time LLMs demonstrated this level of autonomous problem-solving in one of the toughest hacking competitions. The “ico” challenge involved reverse engineering a large, x86-64 server binary with no position-independent executable (PIE) or stack canary protections, allowing for exploitable buffer overflows. The binary spun up a server on port 4265 and featured a complicated virtual machine dispatch loop, making it a substantial reverse engineering and exploitation task, typically demanding expert manual analysis. The team leveraged a cutting-edge GPT-5 model integrated with IDA Pro’s MCP (Modular Command Protocol) server via the Cursor platform, enabling the LLM to interact directly with the binary’s disassembly and gradually piece together the protocol and memory layout over a sustained, fully automated session. The model generated multiple exploit scripts, progressively uncovering how the server loaded a secret flag into memory and packaged it in a metadata response. While the initial AI-generated exploit didn’t immediately capture the flag, iterative refinements produced a robust parser and interaction script that revealed important internal details of the challenge, overcoming obstacles like encrypted metadata formats. This breakthrough validates the growing role of advanced LLMs as autonomous reverse engineering assistants capable of handling real-world, complex binaries in high-stakes security contexts. It highlights how AI can augment elite hacking workflows by accelerating understanding of unfamiliar codebases and crafting initial exploit attempts, potentially reshaping vulnerability research and security CTF training methodologies.