Vulnerability classification (CVSS) in Cybersecurity - Mini Project: Build & Apply

Vulnerability Classification Using CVSS

📖 Scenario: You work in a cybersecurity team that needs to classify software vulnerabilities to understand their severity. You will use the Common Vulnerability Scoring System (CVSS) to organize vulnerabilities by their scores.

🎯 Goal: Create a simple classification system that groups vulnerabilities by their CVSS score ranges: Low, Medium, High, and Critical.

📋 What You'll Learn

Create a dictionary called vulnerabilities with exact CVSS scores for given vulnerabilities

Create a variable called classification as an empty dictionary to hold groups

Use a for loop with variables vuln and score to iterate over vulnerabilities.items()

Add the correct severity label to each vulnerability based on its CVSS score using the exact ranges

💡 Why This Matters

🌍 Real World

Security teams use CVSS scores to prioritize fixing vulnerabilities based on their severity to protect systems effectively.

💼 Career

Understanding how to classify and organize vulnerabilities by severity is essential for cybersecurity analysts and engineers to manage risks.

1

Create the vulnerabilities dictionary

Create a dictionary called vulnerabilities with these exact entries: 'SQL Injection': 9.8, 'Cross-Site Scripting': 6.1, 'Information Disclosure': 4.3, 'Denial of Service': 7.5, 'Buffer Overflow': 10.0.

Cybersecurity

# Create the vulnerabilities dictionary with exact CVSS scores
# Your code here

Hint

Use curly braces to create a dictionary and separate each entry with a comma.

2

Create an empty classification dictionary

Create an empty dictionary called classification to store vulnerabilities grouped by severity levels.

Cybersecurity

vulnerabilities = {
    'SQL Injection': 9.8,
    'Cross-Site Scripting': 6.1,
    'Information Disclosure': 4.3,
    'Denial of Service': 7.5,
    'Buffer Overflow': 10.0
}
# Create an empty dictionary called classification
# Your code here

Hint

Use empty curly braces to create an empty dictionary.

3

Classify vulnerabilities by CVSS score

Use a for loop with variables vuln and score to iterate over vulnerabilities.items(). Inside the loop, assign a severity label to each vulnerability based on its CVSS score: score < 4.0 is 'Low', 4.0 <= score < 7.0 is 'Medium', 7.0 <= score < 9.0 is 'High', and score >= 9.0 is 'Critical'.

Cybersecurity

vulnerabilities = {
    'SQL Injection': 9.8,
    'Cross-Site Scripting': 6.1,
    'Information Disclosure': 4.3,
    'Denial of Service': 7.5,
    'Buffer Overflow': 10.0
}

classification = {}

# Use a for loop to classify vulnerabilities by score
# Your code here

Hint

Use if-elif-else statements inside the loop to assign severity labels.

4

Add vulnerabilities to classification groups

Inside the for loop, add each vulnerability to the classification dictionary under its severity label. If the label does not exist as a key, create a new list. Append the vulnerability name to the list for its severity.

Cybersecurity

vulnerabilities = {
    'SQL Injection': 9.8,
    'Cross-Site Scripting': 6.1,
    'Information Disclosure': 4.3,
    'Denial of Service': 7.5,
    'Buffer Overflow': 10.0
}

classification = {}

for vuln, score in vulnerabilities.items():
    if score < 4.0:
        severity = 'Low'
    elif 4.0 <= score < 7.0:
        severity = 'Medium'
    elif 7.0 <= score < 9.0:
        severity = 'High'
    else:
        severity = 'Critical'
    # Add vulnerability to classification dictionary
    # Your code here

Hint

Check if the severity key exists in the dictionary. If not, create a list. Then add the vulnerability to that list.

Practice

1. What does the CVSS Base Score primarily measure in vulnerability classification?

easy

A. The inherent severity of a vulnerability without considering time or environment

B. The current exploitability of a vulnerability based on available patches

C. The impact of a vulnerability on a specific organization's environment

D. The financial cost of fixing a vulnerability

Solution

1. Step 1: Understand CVSS score components

   CVSS scores have three parts: Base, Temporal, and Environmental. The Base Score measures the fundamental severity of a vulnerability.

2. Step 2: Identify the role of the Base Score

   The Base Score reflects the intrinsic characteristics of a vulnerability that do not change over time or across different environments.

3. Final Answer:

   The inherent severity of a vulnerability without considering time or environment -> Option A

4. Quick Check:

   Base Score = inherent severity [OK]

Hint: Base Score = core severity, ignore time and environment [OK]

Common Mistakes:

• Confusing Base Score with Temporal or Environmental scores
• Thinking Base Score changes over time
• Assuming Base Score includes organizational impact

2. Which of the following is the correct format for a CVSS v3.1 vector string?

easy

A. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

B. CVSS-3.1-AV:N-AC:L-PR:N-UI:N-S:U-C:H-I:H-A:H

C. CVSS3.1:AV=N;AC=L;PR=N;UI=N;S=U;C=H;I=H;A=H

D. CVSSv3.1[AV:N,AC:L,PR:N,UI:N,S:U,C:H,I:H,A:H]

Solution

1. Step 1: Recall CVSS v3.1 vector string syntax

   The official CVSS v3.1 vector string starts with "CVSS:3.1" followed by slash-separated metric abbreviations and values.

2. Step 2: Compare options to official format

   CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H matches the correct format exactly, using slashes and colons as separators.

3. Final Answer:

   CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H -> Option A

4. Quick Check:

   Correct CVSS v3.1 vector format = CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H [OK]

Hint: Look for 'CVSS:3.1' prefix and slash separators [OK]

Common Mistakes:

• Using dashes or semicolons instead of slashes
• Missing the 'CVSS:3.1' prefix
• Incorrect separator characters

3. Given a vulnerability with the following CVSS v3.1 Base metrics: Attack Vector (AV) = Network, Attack Complexity (AC) = Low, Privileges Required (PR) = None, User Interaction (UI) = None, Scope (S) = Unchanged, Confidentiality (C) = High, Integrity (I) = High, Availability (A) = High, what is the approximate Base Score?

medium

A. 5.0

B. 7.5

C. 9.8

D. 3.2

Solution

1. Step 1: Identify metric values and their impact

   AV: Network (high impact), AC: Low (easy to exploit), PR: None (no privileges needed), UI: None (no user interaction), S: Unchanged, C/I/A: High impact on confidentiality, integrity, availability.

2. Step 2: Use CVSS v3.1 calculator logic

   These metrics correspond to a critical vulnerability with a Base Score near 9.8, indicating very high severity.

3. Final Answer:

   9.8 -> Option C

4. Quick Check:

   Critical metrics with no privileges and high impact = 9.8 [OK]

Hint: High impact + no privileges + network vector = ~9.8 score [OK]

Common Mistakes:

• Underestimating score by ignoring high impact metrics
• Confusing Scope Unchanged with Changed
• Mixing up privileges required levels

4. A security analyst notices a CVSS vector string: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N. What is the main error in interpreting this vector?

medium

A. Thinking privileges are required when they are not

B. Believing the attack vector is Network instead of Local

C. Ignoring that the scope is Changed, affecting impact

D. Assuming the vulnerability requires no user interaction

Solution

1. Step 1: Analyze the UI (User Interaction) metric

   The vector shows UI:R, meaning user interaction is Required, not None.

2. Step 2: Identify common misinterpretation

   Assuming UI:N (no user interaction) would be incorrect here; the vulnerability needs user action to exploit.

3. Final Answer:

   Assuming the vulnerability requires no user interaction -> Option D

4. Quick Check:

   UI:R means user interaction required, not none [OK]

Hint: Check UI metric carefully: R means user interaction required [OK]

Common Mistakes:

• Ignoring UI:R and assuming no user action needed
• Mixing up AV:L (Local) with Network
• Overlooking Scope Changed impact

5. An organization wants to prioritize fixing vulnerabilities that have a high CVSS Environmental Score but a medium Base Score. Which approach best explains this prioritization?

hard

A. Fix only vulnerabilities with the highest Base Score regardless of environment

B. Focus on vulnerabilities that impact the organization's specific environment more severely, even if their general severity is medium

C. Ignore Environmental Scores and focus on Temporal Scores for patch urgency

D. Prioritize vulnerabilities with low Base Scores to reduce workload

Solution

1. Step 1: Understand Environmental Score purpose

   The Environmental Score adjusts the Base Score to reflect how a vulnerability affects a specific organization's environment, considering factors like system importance and security controls.

2. Step 2: Apply prioritization logic

   Prioritizing vulnerabilities with high Environmental Scores means focusing on those that pose greater risk in the organization's context, even if their Base Score is only medium.

3. Final Answer:

   Focus on vulnerabilities that impact the organization's specific environment more severely, even if their general severity is medium -> Option B

4. Quick Check:

   Environmental Score = org-specific risk priority [OK]

Hint: Environmental Score shows real risk to your organization [OK]

Common Mistakes:

• Ignoring Environmental Scores in prioritization
• Confusing Temporal Score with Environmental Score
• Assuming Base Score alone dictates fix order