What is Exploit Prediction Scoring System (EPSS)?

What is Exploit Prediction Scoring System (EPSS)?

Dec 8, 2023

In this video, Patrick Garrity, Cybersecurity Researcher and VP at Nucleus, deep dives into the public preview of the Exploit Prediction Scoring System (EPSS).

The Exploit Prediction Scoring System (EPSS) is a data-driven effort for estimating the likelihood (probability) that a software vulnerability will be exploited in the wild. The goal of EPSS is to assist network defenders to better prioritize vulnerability remediation efforts. While other industry standards such as CVSS have been useful for capturing innate characteristics of a vulnerability and provide measures of severity, they are limited in their ability to assess threat. EPSS fills that gap because it uses current threat information from CVE and real-world exploit data.

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited. So let’s look at an example of CVE’s and their EPSS scores. So here we can see the EPSS scores associated with CVE’s which are between 0 and 1 and you can easily prioritize vulnerabilities based on their score. Additionally EPSS also provides a percentile which is simply the percentile of vulnerabilities that score equal or above the EPSS score across all CVE’s w/ EPSS scores.

Key Takeaways:

  • EPSS is a data-driven system that estimates the probability of software vulnerability exploitation.
  • EPSS scores range from 0 to 1, with higher scores indicating a greater likelihood of exploitation.
  • EPSS is best used when there is no other evidence of active exploitation.
  • EPSS scores can be accessed through the EPSs API or by using security products that have incorporated EPSs.
  • Different approaches to using EPSs include prioritizing vulnerabilities based on work effort available and setting scoring thresholds based on risk tolerance.