Abstract
Current frameworks for evaluating security bug severity, such as the Common Vulnerability Scoring System (CVSS), prioritize the ratio of exploitability to impact. This paper suggests that the above approach measures the "known knowns" but inadequately addresses the "known unknowns" especially when there exist multiple possible exploit paths and side effects, which introduce significant uncertainty. This paper introduces the concept of connectedness, which measures how strongly a security bug is connected with different entities, thereby reflecting the uncertainty of impact and the exploit potential. This work highlights the critical but underappreciated role connectedness plays in severity assessments.