scripts/cvss.py

#!/usr/bin/env python3
"""CVSS 3.1 base-score computation + vector builder.

Implements the official FIRST CVSS v3.1 specification formulas so every
benchmark record carries a mathematically consistent vector and score.
Reference: https://www.first.org/cvss/v3.1/specification-document
"""
from __future__ import annotations


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}   # scope unchanged
PR_C = {"N": 0.85, "L": 0.68, "H": 0.50}   # scope changed
UI = {"N": 0.85, "R": 0.62}
CIA = {"H": 0.56, "L": 0.22, "N": 0.0}


def _roundup(value: float) -> float:
    """CVSS roundup: ceil(value * 10) / 10, with a 0-floor."""
    int_input = round(value * 100000)
    if int_input % 10000 == 0:
        return int_input / 100000.0
    return (round((int_input / 10000)) + 1) / 10.0


def severity_from_score(score: float) -> str:
    if score == 0.0:
        return "None"
    if score < 4.0:
        return "Low"
    if score < 7.0:
        return "Medium"
    if score < 9.0:
        return "High"
    return "Critical"


def compute_base_vector(
    *,
    av: str = "N",
    ac: str = "L",
    pr: str = "N",
    ui: str = "N",
    s: str = "U",
    c: str = "H",
    i: str = "H",
    a: str = "H",
) -> tuple[str, float]:
    """Return (CVSS:3.1/... vector string, base_score float)."""
    av, ac, pr, ui, s, c, i, a = (x.upper() for x in (av, ac, pr, ui, s, c, i, a))
    vector = f"CVSS:3.1/AV:{av}/AC:{ac}/PR:{pr}/UI:{ui}/S:{s}/C:{c}/I:{i}/A:{a}"

    if s == "C":
        pr_val = PR_C[pr]
    else:
        pr_val = PR_U[pr]

    iss = 1 - ((1 - CIA[c]) * (1 - CIA[i]) * (1 - CIA[a]))
    if s == "U":
        impact = 6.42 * iss
    else:
        impact = 7.52 * (iss - 0.029) - 3.25 * (iss * 0.9731 - 0.02) ** 13

    exploitability = 8.22 * AV[av] * AC[ac] * pr_val * UI[ui]

    if impact <= 0:
        score = 0.0
    elif s == "U":
        score = _roundup(min(impact + exploitability, 10.0))
    else:
        score = _roundup(min(1.08 * (impact + exploitability), 10.0))

    return vector, round(score, 1)


def cvss_for(vuln_key: str, difficulty: str) -> tuple[str, float]:
    """Hand-tuned default CVSS vectors per vulnerability archetype.

    'difficulty' nudges PR/UI slightly: enterprise examples tend to require
    a foothold or user interaction, so the score is realistic not maximal.
    Returns (vector, score).
    """
    enterprise = difficulty in ("Real-world enterprise", "Expert")
    base = _DEFAULT_VECTORS.get(vuln_key, _DEFAULT_VECTORS["__default__"])
    av, ac, pr, ui, s, c, i, a = [base[f"AV"], base["AC"], base["PR"], base["UI"],
                                  base["S"], base["C"], base["I"], base["A"]]
    # Real-world enterprise scenarios often require low-priv/UI foothold.
    if enterprise and pr == "N":
        pr = "L"
    if enterprise and ui == "N":
        ui = "R"
    return compute_base_vector(av=av, ac=ac, pr=pr, ui=ui, s=s, c=c, i=i, a=a)


# Default vectors keyed by vulnerability_name (normalized lower). Each maps to
# the dominant realistic exploitability/impact profile for that weakness.
_DEFAULT_VECTORS = {
    "__default__": {"AV": "N", "AC": "L", "PR": "N", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "H"},
    "sql injection": {"AV": "N", "AC": "L", "PR": "N", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "H"},
    "cross-site scripting": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "C", "C": "L", "I": "L", "A": "N"},
    "ssrf": {"AV": "N", "AC": "L", "PR": "N", "UI": "N", "S": "C", "C": "H", "I": "L", "A": "L"},
    "command injection": {"AV": "N", "AC": "L", "PR": "N", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "H"},
    "path traversal": {"AV": "N", "AC": "L", "PR": "N", "UI": "N", "S": "U", "C": "H", "I": "N", "A": "N"},
    "xml external entity": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "U", "C": "H", "I": "L", "A": "L"},
    "insecure direct object reference": {"AV": "N", "AC": "L", "PR": "L", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "N"},
    "broken access control": {"AV": "N", "AC": "L", "PR": "L", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "N"},
    "broken authentication": {"AV": "N", "AC": "L", "PR": "N", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "N"},
    "broken authorization": {"AV": "N", "AC": "L", "PR": "L", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "N"},
    "jwt vulnerabilities": {"AV": "N", "AC": "H", "PR": "N", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "N"},
    "oauth vulnerabilities": {"AV": "N", "AC": "H", "PR": "N", "UI": "R", "S": "U", "C": "H", "I": "H", "A": "N"},
    "session management": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "U", "C": "H", "I": "H", "A": "N"},
    "cross-site request forgery": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "U", "C": "H", "I": "H", "A": "N"},
    "insecure file upload": {"AV": "N", "AC": "L", "PR": "N", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "H"},
    "insecure deserialization": {"AV": "N", "AC": "L", "PR": "N", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "H"},
    "open redirect": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "C", "C": "L", "I": "L", "A": "N"},
    "race condition": {"AV": "N", "AC": "H", "PR": "L", "UI": "N", "S": "U", "C": "L", "I": "H", "A": "L"},
    "insecure cryptography": {"AV": "N", "AC": "H", "PR": "N", "UI": "N", "S": "U", "C": "H", "I": "N", "A": "N"},
    "hardcoded secrets": {"AV": "N", "AC": "L", "PR": "L", "UI": "N", "S": "U", "C": "H", "I": "N", "A": "N"},
    "business logic": {"AV": "N", "AC": "L", "PR": "L", "UI": "R", "S": "U", "C": "H", "I": "H", "A": "N"},
    "missing rate limiting": {"AV": "N", "AC": "L", "PR": "N", "UI": "N", "S": "U", "C": "N", "I": "L", "A": "H"},
    "sensitive data logging": {"AV": "L", "AC": "L", "PR": "L", "UI": "N", "S": "U", "C": "H", "I": "N", "A": "N"},
    "header injection": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "C", "C": "L", "I": "L", "A": "N"},
    "prompt injection": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "C", "C": "H", "I": "H", "A": "L"},
    "rag security": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "C", "C": "H", "I": "L", "A": "L"},
    "mcp security": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "C", "C": "H", "I": "H", "A": "L"},
    "ai agent security": {"AV": "N", "AC": "L", "PR": "N", "UI": "R", "S": "C", "C": "H", "I": "H", "A": "H"},
    "graphql security": {"AV": "N", "AC": "L", "PR": "L", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "N"},
    "rest api security": {"AV": "N", "AC": "L", "PR": "L", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "N"},
    "grpc security": {"AV": "N", "AC": "L", "PR": "L", "UI": "N", "S": "U", "C": "H", "I": "H", "A": "N"},
    "cloud misconfiguration": {"AV": "N", "AC": "L", "PR": "L", "UI": "N", "S": "C", "C": "H", "I": "H", "A": "H"},
    "kubernetes security": {"AV": "N", "AC": "L", "PR": "L", "UI": "N", "S": "C", "C": "H", "I": "H", "A": "H"},
    "docker security": {"AV": "L", "AC": "L", "PR": "L", "UI": "N", "S": "C", "C": "H", "I": "H", "A": "H"},
}