The Exploit Prediction Scoring System (EPSS) has emerged as a crucial tool in vulnerability management, providing security teams with data-driven insights into the likelihood of a vulnerability being exploited in the wild. On March 17, 2025, the Forum of Incident Response and Security Teams (FIRST) released EPSS Version 4, introducing significant improvements to its predictive capabilities.

In this blog, we will explore what EPSS is, how it has evolved over the years, and what’s new in Version 4 that makes it more effective in prioritizing vulnerabilities.

What is EPSS?

EPSS is a machine-learning-driven scoring system designed to help security professionals prioritize vulnerabilities based on their real-world exploitability. Unlike the Common Vulnerability Scoring System (CVSS), which focuses on theoretical severity, EPSS analyzes real-world exploitation data to determine the probability of a vulnerability being actively exploited.

Why EPSS Matters

With thousands of new vulnerabilities emerging each year, organizations cannot patch everything. EPSS provides a data-driven approach that enables security teams to focus their remediation efforts on the vulnerabilities most likely to be exploited, reducing risk efficiently.

Evolution of EPSS

EPSS has undergone multiple iterations to refine its accuracy and effectiveness:

• EPSS v1 (2018): The initial version used a simple logistic regression model with 16 variables, making it easy to implement but limited in predictive accuracy.
• EPSS v2 (March 2022): Introduced machine learning with over 1,000 variables, improving accuracy significantly.
• EPSS v3 (March 2023): Further enhancements were made, increasing the number of variables to around 1,500 and refining data sources.
• EPSS v4 (March 2025): The latest iteration introduces substantial improvements in data quality, exploit intelligence, and threat context analysis.

What’s New in EPSS v4?

EPSS v4 brings several advancements that make it more powerful and effective in predicting exploitability:

1. Expanded Exploit Intelligence

EPSS v4 now monitors real-world exploitation data for over 10,000 vulnerabilities each month, significantly improving prediction accuracy. The increased dataset helps security teams stay ahead of evolving threats.

2. Integration of Malware & Endpoint Telemetry

One of the biggest improvements in EPSS v4 is the incorporation of malware intelligence and endpoint detection telemetry. This allows the system to:

• Detect exploit attempts earlier.
• Identify patterns associated with exploitation activity.
• Improve prediction accuracy by correlating exploit attempts with real-world attacks.

3. Broader Threat Context

EPSS v4 leverages diverse data sources, including:

• Threat intelligence feeds.
• Security blogs and forums.
• Public exploit repositories.

This expanded context enhances the model’s ability to predict which vulnerabilities will be actively targeted by attackers.

4. Improved Vulnerability Categorization

EPSS v4 refines its classification approach by:

• Grouping vulnerabilities under the top 22 Common Weakness Enumeration (CWE) categories.
• Excluding REJECTED CVEs from analysis, reducing noise in predictions.

5. More Efficient Prioritization Compared to CVSS

EPSS v4 demonstrates significant efficiency improvements over traditional CVSS-based prioritization. Here’s how:

• CVSS 7+ prioritization requires patching 50% of known CVEs to achieve 74.6% exploit coverage, with only 6% efficiency.
• EPSS v4 achieves similar coverage by patching just 6% of vulnerabilities, increasing efficiency to 47%.

These improvements allow organizations to focus their efforts on the vulnerabilities that truly matter, optimizing resource allocation and risk mitigation.

Why EPSS v4 is a Game Changer for Security Teams

EPSS v4 makes vulnerability management more precise and actionable by:

• Reducing false positives: Security teams can avoid wasting time on low-risk vulnerabilities.
• Improving threat awareness: The broader data sources provide a more accurate picture of exploitability.
• Enhancing remediation efficiency: Organizations can allocate resources effectively to mitigate real threats.

Conclusion

EPSS v4 represents a major leap forward in vulnerability management. By leveraging real-world exploit data, integrating malware telemetry, and improving classification techniques, it offers a more efficient and accurate way to prioritize vulnerabilities. Security teams looking to enhance their remediation strategies should consider incorporating EPSS v4 into their risk assessment frameworks.

With cyber threats evolving rapidly, having a tool like EPSS v4 ensures that organizations stay ahead of attackers and focus their efforts where they matter most.

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