CVE CVSS Calculator

import math

# CVSS v3.1 Base Score Calculator
WEIGHTS = {
    'AV': {'N': 0.85, 'A': 0.62, 'L': 0.55, 'P': 0.20},
    'AC': {'L': 0.77, 'H': 0.44},
    'PR_U': {'N': 0.85, 'L': 0.62, 'H': 0.27},  # Unchanged scope
    'PR_C': {'N': 0.85, 'L': 0.68, 'H': 0.50},  # Changed scope
    'UI': {'N': 0.85, 'R': 0.62},
    'CIA': {'N': 0.00, 'L': 0.22, 'H': 0.56},
}

def roundup(x: float) -> float:
    """CVSS-specific roundup to 1 decimal place."""
    return math.ceil(x * 10) / 10

def calculate_cvss_base(av, ac, pr, ui, scope, c_impact, i_impact, a_impact) -> tuple[float, str]:
    """Calculate CVSS v3.1 Base Score."""
    scope_changed = scope == 'C'
    pr_w = WEIGHTS['PR_C'][pr] if scope_changed else WEIGHTS['PR_U'][pr]

    iss = 1 - (1 - WEIGHTS['CIA'][c_impact]) * (1 - WEIGHTS['CIA'][i_impact]) * (1 - WEIGHTS['CIA'][a_impact])

    if scope_changed:
        impact = 7.52 * (iss - 0.029) - 3.25 * (iss - 0.02) ** 15
    else:
        impact = 6.42 * iss

    exploitability = 8.22 * WEIGHTS['AV'][av] * WEIGHTS['AC'][ac] * pr_w * WEIGHTS['UI'][ui]

    if impact <= 0:
        score = 0.0
    elif scope_changed:
        score = roundup(min(1.08 * (impact + exploitability), 10))
    else:
        score = roundup(min(impact + exploitability, 10))

    # Severity
    severity = 'None' if score == 0 else 'Low' if score < 4 else 'Medium' if score < 7 else 'High' if score < 9 else 'Critical'
    return score, severity

# Example: Critical vulnerability (Log4Shell-like)
score, severity = calculate_cvss_base(
    av='N', ac='L', pr='N', ui='N',  # Network, Low complexity, No privileges, No user interaction
    scope='C',                          # Scope Changed
    c_impact='H', i_impact='H', a_impact='H'  # High CIA impact
)
print(f"Log4Shell-like score: {score} ({severity})")

# Example: Local privilege escalation
score, severity = calculate_cvss_base('L', 'L', 'L', 'N', 'U', 'H', 'H', 'N')
print(f"Local privesc: {score} ({severity})")