LLM4Vuln: A Unified Evaluation Framework for Decoupling and Enhancing LLMs' Vulnerability Reasoning

LLMs have demonstrated significant potential for many downstream tasks, including those requiring human-level intelligence, such as vulnerability detection. However, recent attempts to use LLMs for vulnerability detection are still preliminary, as they lack an in-depth understanding of a subject LLM's vulnerability reasoning capability -- whether it originates from the model itself or from external assistance, such as invoking tool support and retrieving vulnerability knowledge. In this paper, we aim to decouple LLMs' vulnerability reasoning capability from their other capabilities, including the ability to actively seek additional information (e.g., via function calling in SOTA models), adopt relevant vulnerability knowledge (e.g., via vector-based matching and retrieval), and follow instructions to output structured results. To this end, we propose a unified evaluation framework named LLM4Vuln, which separates LLMs' vulnerability reasoning from their other capabilities and evaluates how LLMs' vulnerability reasoning could be enhanced when combined with the enhancement of other capabilities. To demonstrate the effectiveness of LLM4Vuln, we have designed controlled experiments using 75 ground-truth smart contract vulnerabilities, which were extensively audited as high-risk on Code4rena from August to November 2023, and tested them in 4,950 different scenarios across three representative LLMs (GPT-4, Mixtral, and Code Llama). Our results not only reveal ten findings regarding the varying effects of knowledge enhancement, context supplementation, prompt schemes, and models but also enable us to identify 9 zero-day vulnerabilities in two pilot bug bounty programs with over 1,000 USD being awarded.