The coordinated vulnerability disclosure model, widely adopted in open-source software (OSS) organizations, recommends the silent resolution of vulnerabilities without revealing vulnerability information until their public disclosure. However, the inherently public nature of OSS development leads to security fixes becoming publicly available in repositories weeks before the official disclosure of vulnerabilities. This time gap poses a significant security risk to OSS users, as attackers could discover the fix and exploit vulnerabilities before disclosure. Thus, there is a critical need for OSS users to sense fixes as early as possible to address the vulnerability before any exploitation occurs.

In response to this challenge, we introduce EarlyVulnFix, a novel approach designed to identify silent fixes for taint-style vulnerabilities—a persistent class of security weaknesses where attacker-controlled input reaches sensitive operations (sink) without proper sanitization. Leveraging data flow and dependency analysis, our tool distinguishes two types of connections between newly introduced code and sinks, tailored for two common fix scenarios. Our evaluation demonstrates that EarlyVulnFix surpasses state-of-the-art baselines by a substantial margin in terms of F1 score. Furthermore, when applied to the 700 latest commits across seven projects, EarlyVulnFix detected three security fixes before their respective security releases, highlighting its effectiveness in identifying unreported vulnerability fixes in the wild.