"EPSS vs CVSS" Use-Cases Available on OT Sites

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Let's compare EPSS vs CVSS and find out use cases that can be utilized in OT sites.

EPSS (Exploit Prediction Scoring System) is a model that numerically predicts the probability of a known security vulnerability being actually exploited (Exploit Probability).
  • It helps determine which vulnerability to respond to first when there are many vulnerabilities.
  • A supplementary indicator to prioritize vulnerabilities with a high probability of actually being attacked rather than simply having a high CVSS (Vulnerability Severity Score).

Score range: Probability value between 0.0 and 1.0 (or 0% to 100%)
  • Example: EPSS = 0.82 → It means that there is a high probability of actually being exploited in the near future with a probability of 82%


Comparison of EPSS vs. CVSS

FeatureEPSS (Exploit Prediction Scoring System)CVSS (Common Vulnerability Scoring System)
PurposePredicts the likelihood of a vulnerability being exploited in the wild.Measures the severity of vulnerabilities based on impact and exploitability.
Focus AreaUses machine learning and real-world exploit data to assess risk dynamically.Provides a static risk assessment based on the vulnerability’s characteristics.
Scoring ComponentsFactors in exploit availability, attack telemetry, vulnerability metadata, and historical trends.Considers attack vector, complexity, privileges required, and user interaction.
Risk AssessmentHelps predict future exploitation likelihood, guiding proactive defense.Helps prioritize vulnerabilities based on potential damage if exploited.
Update FrequencyContinuously updated with new threat intelligence and exploit trends.Assigned when a CVE is published and remains relatively static unless updated manually.
Use in OT SecurityUseful in ICS/OT environments where predicting likely attacks can help preemptively strengthen defenses.Helps systematically categorize vulnerabilities for structured risk management.


Use-Case: How Security Personnel Can Use EPSS and CVSS in the Field

Scenario: Prioritizing Patch Management in a Power Plant

  • Step 1: Identify Vulnerabilities
     A security analyst in a power plant identifies two vulnerabilities affecting industrial control systems (ICS):

    • Vulnerability A: CVSS score of 9.0 (Critical)
    • Vulnerability B: CVSS score of 7.5 (High)

  • Step 2: Check EPSS Scores

    • Vulnerability A has an EPSS score of 0.02 (2% chance of exploitation in the next 30 days)
    • Vulnerability B has an EPSS score of 0.85 (85% chance of exploitation in the next 30 days)

  • Step 3: Prioritize Actions

    • CVSS suggests patching Vulnerability A first (higher severity).
    • EPSS suggests patching Vulnerability B first (higher likelihood of being exploited soon).
    • The analyst chooses to patch Vulnerability B first, as active exploit attempts are more likely in the near future.

  • Step 4: Additional Mitigations

    • For Vulnerability A, they apply network segmentation and monitoring since no active exploitation is expected soon.
    • For Vulnerability B, they deploy immediate patches, enforce access control restrictions, and enable intrusion detection rules to monitor potential attacks.

Conclusion

EPSS enables security teams to prioritize vulnerabilities based on real-world risk, while CVSS provides a structured method to classify severity. Using both together leads to a smarter, risk-based approach to vulnerability management.


#CPS #OT #XIoT #IoT #IIoT #IoMT #CPSSecurity #OTSecurity #IoTSecurity #CPS보안 #OT보안 #IoT보안

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