Shedding Light on CVSS Scoring Inconsistencies: A User-Centric Study on Evaluating Widespread Security Vulnerabilities

TL;DR

This study investigates the inconsistency of CVSS vulnerability severity scores among users, revealing significant variability and factors influencing assessments, and offers recommendations to improve scoring consistency.

Contribution

It provides a systematic user-centric analysis of CVSS scoring inconsistencies and discusses potential improvements for more reliable vulnerability evaluations.

Findings

68% of users rated the same vulnerabilities differently

Specific CVSS metrics are inconsistently evaluated

Most evaluators recognize CVSS issues but find it useful

Abstract

The Common Vulnerability Scoring System (CVSS) is a popular method for evaluating the severity of vulnerabilities in vulnerability management. In the evaluation process, a numeric score between 0 and 10 is calculated, 10 being the most severe (critical) value. The goal of CVSS is to provide comparable scores across different evaluators. However, previous works indicate that CVSS might not reach this goal: If a vulnerability is evaluated by several analysts, their scores often differ. This raises the following questions: Are CVSS evaluations consistent? Which factors influence CVSS assessments? We systematically investigate these questions in an online survey with 196 CVSS users. We show that specific CVSS metrics are inconsistently evaluated for widespread vulnerability types, including Top 3 vulnerabilities from the "2022 CWE Top 25 Most Dangerous Software Weaknesses" list. In a follow-up survey with 59 participants, we found that for the same vulnerabilities from the main study, 68% of these users gave different severity ratings. Our study reveals that most evaluators are aware of the problematic aspects of CVSS, but they still see CVSS as a useful tool for vulnerability assessment. Finally, we discuss possible reasons for inconsistent evaluations and provide recommendations on improving the consistency of scoring.