---
name: cvss-score-extraction
description: Extract and prioritize CVSS scores from multiple sources in vulnerability reports to ensure the most accurate data is used.
---

# CVSS Score Extraction

Vulnerability reports from tools like Trivy often include CVSS scores from multiple authorities (e.g., NVD, GHSA, RedHat). This skill covers how to extract these scores with a fallback priority.

## CVSS Data Structure in Trivy
Trivy JSON reports store CVSS data in a `CVSS` map within each vulnerability object:

```json
"CVSS": {
  "ghsa": {
    "V3Vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
    "V3Score": 9.8
  },
  "nvd": {
    "V3Vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
    "V3Score": 9.8
  }
}
```

## Extraction Logic
When multiple scores are available, a common priority order is:
1. **NVD (National Vulnerability Database)**: The standard authority.
2. **GHSA (GitHub Security Advisories)**: Often more up-to-date for ecosystem-specific packages.
3. **RedHat/Vendor**: Specific to vendor-patched versions.

### Python Example for Extraction

```python
def extract_cvss(cvss_data):
    if not cvss_data:
        return "N/A"
    
    # Priority: nvd, then ghsa, then others
    for source in ['nvd', 'ghsa']:
        source_data = cvss_data.get(source)
        if source_data:
            score = source_data.get('V3Score') or source_data.get('V2Score')
            if score is not None:
                return score
                
    # Fallback to any available source
    for source_data in cvss_data.values():
        score = source_data.get('V3Score') or source_data.get('V2Score')
        if score is not None:
            return score
            
    return "N/A"
```