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.

EPSS Vulnerability Score and Data #

The EPSS vulnerability score predicts how likely attackers will exploit a vulnerability within the next 30 days. This score allows security teams to focus on vulnerabilities that attackers are most likely to target, making vulnerability management more effective. Instead of relying solely on severity like traditional methods, EPSS provides a more actionable insight by assessing real-world exploitability.

The score ranges between 0 and 1. A score closer to 1 means a higher probability of exploitation, while a score near 0 suggests a much lower risk. For example, a vulnerability with a low CVSS score but a high EPSS score might pose a more immediate threat, since attackers are actively exploiting it. This approach ensures teams address the most urgent risks first, optimizing resource allocation.

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 #

EPSS predicts the likelihood of vulnerability exploitation through a five-step process:

1. Data Collection: Gathering information from sources like NVD, Exploit-DB, and CISA.
2. Exploitation Evidence: Tracking real-world exploitation activity.
3. Model Training: Using machine learning to understand the relationship between vulnerabilities and exploitation.
4. Optimization: Continuously refining the model’s accuracy.
5. Daily Updates: Publishing updated vulnerability scores daily, giving teams real-time insights..

EPSS vs. CVSS: A Stronger Approach #

While CVSS measures vulnerability severity, the Exploit Prediction Scoring System focuses on the likelihood of exploitation. By combining both models, security teams gain a comprehensive understanding of vulnerability risks. On the one hand, CVSS highlights how dangerous a vulnerability is, while on the other hand, the Exploit Prediction Scoring System identifies which vulnerabilities attackers are most likely to target. Therefore, this approach ensures that teams focus on EPSS vulnerabilities posing the greatest real-world threats.

For more on combining EPSS and CVSS, check out Xygeni’s blog on CVE scoring.

Xygeni OSS Security Tools: Powered by EPSS #

At Xygeni, we integrate the Exploit Prediction Scoring System into our Open Source Security (OSS) Tools, enabling teams to tackle vulnerabilities that attackers are most likely to exploit. Here’s how we leverage EPSS to optimize vulnerability management:

• – 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 EPSS-Powered OSS Tools with a Free Demo

Ready to boost your vulnerability management? Xygeni’s OSS tools, powered by EPSS, help you focus on the most critical threats. Request a demo today to see how we can help you stay ahead of attackers

Frequently Asked Questions #