Introduction to Exploit Prediction Scoring System #
Back in Black Hat 2019, the Exploit Prediction Scoring System (EPSS) made its debut. Created by FIRST.org, EPSS helps cybersecurity pros prioritize vulnerabilities based on how likely they are to be exploited. Meanwhile, traditional systems like CVSS focus on how severe a vulnerability is. However, the Exploit Prediction Scoring System goes a step further by addressing real-world risks. It assigns a probability score between 0 and 1, predicting which vulnerabilities attackers are most likely to target over the next 30 days. As a result, this approach helps teams zero in on the most critical vulnerabilities, making patching faster and smarter.
In March 2023, the latest EPSS version (v3) rolled out, boosting performance by 82% in identifying vulnerabilities likely to be exploited. Ultimately, this makes it an essential tool in any security strategy.
Definition:
What is EPSS?
EPSS predicts the likelihood that attackers will exploit a vulnerability within the next 30 days. The score updates daily, helping organizations focus on vulnerabilities that carry the highest risk. Scores range from 0 to 1—higher scores indicate a greater chance of exploitation
EPSS Vulnerability Score and Data #
The EPSS vulnerability score tells you how likely attackers are to exploit a vulnerability in the next 30 days. Unlike traditional systems that only rate severity, EPSS highlights which issues pose the most immediate risk—so your team can fix what matters most.
This score ranges from 0 to 1. A value closer to 1 means attackers are more likely to target it soon. For instance, a bug with a low CVSS score but a high EPSS score might demand urgent attention because attackers are already going after it.
By using EPSS, your team stays focused on real-world threats and improves how you manage vulnerabilities across your pipeline.
The EPSS score pulls data from multiple sources, including:
- CVE identifier: A unique identifier from MITRE’s CVE List that provides key details about each vulnerability.
- EPSS score: A probability score that ranges from 0 to 1, showing the likelihood of exploitation.
- Percentile ranking: This ranks the vulnerability’s score in comparison to others, providing context for its relative risk level.
Beyond real-time scores, EPSS also offers historical data, which allows teams to track risk trends over time and adjust their strategies accordingly. Since EPSS updates daily, security teams can always rely on the most current data to make informed decisions. Additionally, teams can download the data in CSV format, making it easier to analyze vulnerabilities and prioritize remediation efforts.
Overall, the EPSS vulnerability score empowers teams to stay ahead of attackers by focusing on the vulnerabilities that pose the highest risk in real-world scenarios. With daily updates and reliable data from multiple sources, EPSS provides a proactive approach to vulnerability management
How the EPSS Model Works #
Exploit Prediction Scoring System predicts the likelihood of vulnerability exploitation through a five-step process:
- Data Collection: Gathering information from sources like NVD, Exploit-DB, and CISA.
- Exploitation Evidence: Tracking real-world exploitation activity.
- Model Training: Using machine learning to understand the relationship between vulnerabilities and exploitation.
- Optimization: Continuously refining the model’s accuracy.
- Daily Updates: Publishing updated vulnerability scores daily, giving teams real-time insights..
How does EPSS differ from other vulnerability scoring systems like CVSS? #
While it may be true that CVSS focuses on the theoretical impact of vulnerabilities, the Exploit Prediction Scoring System emphasizes the likelihood of exploitation in the real world. By combining both, security teams can make smarter, risk-informed decisions.
- CVSS = how bad could it be
- EPSS = how likely is it to happen
On the one hand, CVSS describes the potential damage a vulnerability can cause. On the other hand, Exploit Prediction Scoring System identifies which vulnerabilities attackers are most likely to exploit in the near term. Therefore, security teams who use both systems together can prioritize vulnerabilities more effectively and fix what truly matters.
For more on combining EPSS and CVSS, check out Xygeni’s blog on CVE scoring or EPSS – a New Standard
Xygeni OSS Security Tools: Powered by EPSS #
At Xygeni, we use the Exploit Prediction Scoring System in our Open Source Security (OSS) Tools to help teams focus on the vulnerabilities attackers are most likely to exploit. Here’s how we use EPSS to make vulnerability management smarter:
- CVE Scoring and EPSS Integration: Our OSS tools combine the Exploit Prediction Scoring System and CVSS to rank vulnerabilities based on their exploitation likelihood. For example, we prioritize vulnerabilities like CVE-2021-44228, which has both a high CVSS score and a high EPSS vulnerability score.
- Advanced Reachability Analysis: We don’t just identify vulnerabilities. We assess whether they are exploitable within your specific environment, ensuring your team focuses on actionable, high-risk threats.
- Real-Time Alerts and Continuous Monitoring: Our OSS tools continuously monitor new vulnerabilities and provide real-time alerts when high-risk vulnerabilities emerge. This proactive approach keeps your team ahead of attackers.
Protect Your Software: Try Xygeni’s OSS Tools with a Free Demo or a Free Trial
Ready to boost your vulnerability management? Xygeni’s OSS tools, powered by EPSS, help you focus on the most critical threats. Request a demo or Give it a try today to see how we can help you stay ahead of attackers
Frequently Asked Questions #
In essence, the EPSS score measures the probability that a vulnerability will be exploited within the next 30 days. Specifically, this score ranges from 0 to 1. Consequently, a higher score signals a greater chance of real-world exploitation—which means security teams can prioritize which vulnerabilities to address first based on actual risk, not just theoretical severity.
EPSS stands for Exploit Prediction Scoring System. In essence, it’s a model that estimates the likelihood of vulnerabilities being exploited. As a result, it helps organizations prioritize security responses based on actual risk.
It update daily to reflect the latest threat intelligence and exploit activity. Consequently, security teams stay aligned with shifting risks—especially in dynamic environments where timing is critical.
You can access exploit prediction scores directly within Xygeni—no need to use separate dashboards. Our platform automatically uses these scores to prioritize vulnerabilities based on real-world risk, so you fix what’s most likely to be exploited first.
