Have We Solved Access Control Vulnerability Detection in Smart Contracts? A Benchmark Study

Access control (AC) vulnerabilities are among the most critical security threats to smart contracts. Despite extensive research, they remain widespread and damaging in the Ethereum ecosystem. To understand and advance the current state-of-the-art (SOTA) in AC vulnerability detection, we first curate a diverse dataset of 180 real-world AC vulnerabilities from CVE entries, DeFiHackLabs incidents, and Code4rena audit reports. Using this dataset, we conduct a systematic benchmark study along three dimensions. First, we develop a cause-based taxonomy and analyze the prevalence and evolution of AC vulnerabilities. Second, we evaluate six SOTA tools, including two from industry and four from academia, revealing low recall (3% to 8%) and significant blind spots. To understand these failures, we examine 1.2 million deployed contracts and uncover practical gaps in AC protection mechanisms overlooked by existing tools. Finally, we assess the potential of large language models (LLMs) for AC vulnerability detection and show that LLMs detect 53-75% of vulnerabilities, outperforming traditional tools but facing challenges such as hallucinations and scalability. Our findings highlight the need for hybrid approaches that combine static analysis with LLM-based semantic reasoning to address the complexity of modern AC vulnerabilities.