In a recent deep dive into vulnerability patch prioritization, alternative tools and frameworks have been explored as potential complements or alternatives to the Common Vulnerability Scoring System (CVSS). One such tool is the Predictive Vulnerability Scoring System (EPSS), introduced at Black Hat USA 2019 by a Special Interest Group (SIG) under FIRST. EPSS aims to predict the likelihood of exploitation based on historical data using logistic regression, analyzing factors such as exploit code availability and affected vendor.
By analyzing over 25,000 vulnerabilities from 2016 to 2018, EPSS creators found that weaponized exploits, specific vendors like Microsoft and Adobe, and the presence of proof-of-concept code contributed significantly to the predictive model. Interestingly, negative correlations were observed for vendors like Google and Apple, suggesting varying exploitation rates based on historical data.
EPSS, originally implemented as a spreadsheet, later transitioned to a centralized architecture with a more advanced machine learning model for improved prediction accuracy within a 30-day window. While EPSS scores are not integrated into the National Vulnerability Database (NVD), they can be accessed through other databases like VulnDB.
Furthermore, the article delves into the limitations and considerations of using EPSS for vulnerability prioritization. It is highlighted that EPSS provides a probability score for general exploitation likelihood, not organization-specific targeting, impact assessment, or exploit incorporation. Transparency concerns surrounding the machine learning model and data access are also discussed.
Additionally, alternative tools and frameworks such as SSVC, KEV Catalog, and CVE Trends are presented as valuable resources for prioritization based on different criteria and decision trees. The potential integration of criminal marketplace data for prioritization is proposed, highlighting the need for further research in this area.
Ultimately, the article emphasizes the importance of combining multiple tools and frameworks for a holistic view of vulnerability prioritization, customization according to organizational context, and the inclusion of additional threat intelligence and risk assessment factors in the decision-making process. Despite the limitations and challenges posed by these tools, their utilization in a strategic, informed manner can enhance a comprehensive vulnerability management strategy.