CVSS v4.0 Interactive Learning Module

1️⃣ What is CVSS v4.0?

The Common Vulnerability Scoring System (CVSS) provides a standardized method to measure the severity of software vulnerabilities. Version 4.0 improves accuracy and adaptability, covering Base, Temporal, and Environmental metrics.

Base Metrics: Intrinsic properties of a vulnerability (constant over time).
Temporal Metrics: Factors that change over time (e.g., exploit code availability).
Environmental Metrics: Context-specific impact (depends on organization’s environment).

2️⃣ Base Metrics Overview

Metric	Description	Possible Values
Attack Vector (AV)	How far an attacker can reach	Network (0.85), Adjacent (0.62), Local (0.55), Physical (0.20)
Attack Complexity (AC)	Conditions required beyond attacker control	Low (0.77), High (0.44)
Privileges Required (PR)	Level of privileges required	None (0.85), Low (0.62), High (0.27)
User Interaction (UI)	Does the victim need to act?	None (0.85), Required (0.62)
Confidentiality (C)	Impact on confidentiality	None (0.0), Low (0.22), High (0.56)
Integrity (I)	Impact on data integrity	None (0.0), Low (0.22), High (0.56)
Availability (A)	Impact on system availability	None (0.0), Low (0.22), High (0.56)

2️⃣ Base Metrics Calculator

Select values for each metric to compute the Base Score.

Metric	Selection
Attack Vector (AV)
Attack Complexity (AC)
Privileges Required (PR)
User Interaction (UI)
Confidentiality (C)
Integrity (I)
Availability (A)

Select metrics and click Calculate.

3️⃣ Temporal Metrics Calculator

These represent how the exploit and remediation status affect the Base Score.

Metric	Selection
Exploit Code Maturity (E)
Remediation Level (RL)
Report Confidence (RC)

Compute Base first, then apply temporal factors.

4️⃣ Environmental Metrics Calculator

These represent the importance of the impacted system in the organization’s environment.

Metric	Selection
Confidentiality Requirement (CR)
Integrity Requirement (IR)
Availability Requirement (AR)

Compute Temporal first, then adjust by environment.

5️⃣ Example: Critical Web Server Vulnerability

Scenario: A remote code execution flaw allows attackers to gain full system control remotely without authentication.

AV=Network, AC=Low, PR=None, UI=None
C=High, I=High, A=High
E=Functional, RL=Temporary Fix, RC=Confirmed
CR=High, IR=High, AR=Medium

Final Environmental Score ≈ 9.8 (Critical)

Explain the Formula for Base Score Calculation

Base Score = round_to_1_decimal((0.6 × Impact) + (0.4 × Exploitability) - 1.5)

Step-by-Step Example

Scenario

A web application allows SQL injection through a poorly sanitized user input field.

Step 1: Determine Base Metrics

Attack Vector (AV): Network (0.85)
Attack Complexity (AC): Low (0.77)
Privileges Required (PR): None (0.85)
User Interaction (UI): None (0.85)
Scope (S): Unchanged (1.00)
Confidentiality Impact (C): High (0.56)
Integrity Impact (I): High (0.56)
Availability Impact (A): Low (0.22)

Step 2: Calculate Impact

Impact Calculation:
Impact = 1 - [(1 - C) × (1 - I) × (1 - A)]
Impact = 1 - [(1 - 0.56) × (1 - 0.56) × (1 - 0.22)]
Impact = 1 - [0.44 × 0.44 × 0.78] = 0.863872

Step 3: Calculate Exploitability

Exploitability Calculation:
Exploitability = 8.22 × AV × AC × PR × UI
Exploitability = 8.22 × (0.85 + 0.77 + 0.85 + 0.85)
Exploitability = 8.22 × 3.32 = 27.31

Step 4: Calculate Base Score

Base Score Calculation:
Base Score = round_to_1_decimal((0.6 × Impact) + (0.4 × Exploitability) - 1.5)
Base Score = round_to_1_decimal((0.6 × 0.863872) + (0.4 × 27.31) - 1.5)
Base Score = round_to_1_decimal(0.5183232 + 10.924 - 1.5) = 9.9

Final Score

The calculated CVSS Base Score for this vulnerability is 9.9, indicating a high severity level.

🌐 Explore CVSS Calculators

Here are some reliable online tools to calculate and analyze Common Vulnerability Scoring System (CVSS) scores. You can use these calculators to explore how changing metric values affects Base, Temporal, and Environmental scores.

FIRST CVSS v4.0 Calculator

The official calculator from the Forum of Incident Response and Security Teams (FIRST).

Open Calculator

NIST CVSS v3.1 Calculator

NIST’s implementation of the CVSS v3.1 scoring system with reference links to NVD entries.

Try It Now

Vulnogram CVSS Calculator

A simplified calculator with a user-friendly interface for quick vulnerability scoring.

Visit Vulnogram

SecOps : Understanding CVSS Calculator

Detailed Explanation of how the score is calculated

Check SecOps

💡 Tip: I encourage you to test the same vulnerability across multiple calculators and observe score differences.