Automatic Library Fuzzing through API Relation Evolvement

Software libraries are foundational components in modern software ecosystems. Vulnerabilities within these libraries pose significant security threats. Fuzzing is a widely used technique for uncovering software vulnerabilities. However, its application to software libraries poses considerable challenges, necessitating carefully crafted drivers that reflect diverse yet correct API usages. Existing works on automatic library fuzzing either suffer from high false positives due to API misuse caused by arbitrarily generated API sequences, or fail to produce diverse API sequences by overly relying on existing code snippets that express restricted API usages, thus missing deeper API vulnerabilities. This work proposes NEXZZER, a new fuzzer that automatically detects vulnerabilities in libraries. NEXZZER employs a hybrid relation learning strategy to continuously infer and evolve API relations, incorporating a novel driver architecture to augment the testing coverage of libraries and facilitate deep vulnerability discovery. We evaluated NEXZZER across 18 libraries and the Google Fuzzer Test Suite. The results demonstrate its considerable advantages in code coverage and vulnerability-finding capabilities compared to prior works. NEXZZER can also automatically identify and filter out most API misuse crashes. Moreover, NEXZZER discovered 27 previously unknown vulnerabilities in well-tested libraries, including OpenSSL and libpcre2. At the time of writing, developers have confirmed 24 of them, and 9 were fixed because of our reports.