Understanding CVSS

CVSS is maintained by the Forum of Incident Response and Security Teams (FIRST) and provides a way to assess and communicate the characteristics and severity of software vulnerabilities. The system produces a numerical score that represents the overall severity of a vulnerability, ranging from 0.0 (no severity) to 10.0 (critical severity).

CVSS Scoring System

CVSS uses three metric groups to calculate a vulnerability’s score:

Base Score Metrics

These metrics represent the intrinsic characteristics of a vulnerability that are constant over time and across user environments:

• Attack Vector (AV): How the vulnerability can be exploited (Network, Adjacent, Local, Physical)
• Attack Complexity (AC): Conditions beyond the attacker’s control that must exist for exploitation
• Privileges Required (PR): Level of privileges an attacker must possess before successfully exploiting the vulnerability
• User Interaction (UI): Whether the vulnerability requires a user to take some action
• Scope (S): Whether a successful attack impacts resources beyond the vulnerable component
• Confidentiality Impact (C): Impact on the confidentiality of information
• Integrity Impact (I): Impact on the integrity of information
• Availability Impact (A): Impact on the availability of the affected system

Temporal Score Metrics

These metrics change over time as the vulnerability ages:

• Exploit Code Maturity (E): How likely it is that exploit code is available
• Remediation Level (RL): The level of remediation available
• Report Confidence (RC): How confident the vulnerability report is

Environmental Score Metrics

These metrics are specific to a user’s environment:

• Confidentiality Requirement (CR): Importance of confidentiality in the affected system
• Integrity Requirement (IR): Importance of integrity in the affected system
• Availability Requirement (AR): Importance of availability in the affected system
• Modified Base Metrics: Any modifications to the base metrics based on the environment

CVSS Score Ranges

CVSS scores are categorized into severity levels:

• 0.0: None
• 0.1-3.9: Low
• 4.0-6.9: Medium
• 7.0-8.9: High
• 9.0-10.0: Critical

Example CVSS Calculation

For a vulnerability with the following characteristics:

• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Changed (S:C)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

This would result in a CVSS Base Score of 9.8 (Critical).

CVSS vs. CVE

While CVSS and CVE are related, they serve different purposes:

• CVE (Common Vulnerabilities and Exposures): Provides a unique identifier for a specific vulnerability
• CVSS: Provides a standardized way to score and communicate the severity of that vulnerability

A CVE entry will often include a CVSS score to help organizations understand the severity of the vulnerability.

Using CVSS in Vulnerability Management

Prioritization

CVSS scores help organizations prioritize which vulnerabilities to address first:

• Critical (9.0-10.0): Immediate attention required
• High (7.0-8.9): Address within days to weeks
• Medium (4.0-6.9): Address within weeks to months
• Low (0.1-3.9): Address as resources permit

Risk Assessment

CVSS scores can be used in risk assessments to:

• Determine the potential impact of vulnerabilities
• Allocate resources for remediation efforts
• Communicate risk to stakeholders
• Comply with security frameworks and regulations

Integration with Security Tools

Many security tools and platforms integrate CVSS scoring to:

• Automatically prioritize vulnerabilities in scan results
• Generate risk reports
• Trigger automated workflows based on severity
• Provide dashboards and metrics

CVSS in Service Mesh and Cloud-Native Security

In the context of service mesh and cloud-native applications, CVSS is particularly important because:

Microservices Complexity

• Multiple services increase the attack surface
• Vulnerabilities in one service can affect others
• CVSS helps prioritize which service vulnerabilities to address first

Container Security

• Container images may contain multiple vulnerabilities
• CVSS scores help determine which containers to update first
• Integration with container scanning tools provides automated prioritization

Zero Trust Architecture

• CVSS scores inform access control decisions
• High-severity vulnerabilities may require additional security measures
• Helps maintain the principle of “never trust, always verify”

Best Practices for Using CVSS

1. Don’t Rely Solely on CVSS Scores

• Consider your specific environment and context
• Factor in business impact and asset criticality
• Use CVSS as one input in your risk assessment

2. Regular Updates

• CVSS scores may change over time as new information becomes available
• Regularly review and update vulnerability assessments
• Monitor for changes in exploit availability and remediation status

3. Integration with Other Frameworks

• Combine CVSS with other security frameworks (NIST, ISO 27001, etc.)
• Use CVSS scores in compliance reporting
• Integrate with your overall security program

4. Communication

• Use CVSS scores to communicate risk to stakeholders
• Provide context for non-technical audiences
• Include CVSS scores in security reports and dashboards

Related Resources

• What Is a CVE (Common Vulnerability and Exposure)? - Understanding CVE identifiers
• What Is the Difference Between CVE and CVSS? - Understanding the relationship between CVEs and CVSS
• What Are the Benefits of CVEs? - Understanding the value of vulnerability tracking
• Cybersecurity Vulnerability Management - Best practices for managing vulnerabilities
• Tetrate Security Solutions - Enterprise security with service mesh

Learn More

For organizations looking to improve their vulnerability management:

• CVSS Calculator - Official CVSS calculator
• FIRST CVSS Documentation - Official CVSS documentation
• Tetrate Security Assessment - Evaluate your security posture
• Enterprise Security Support - Professional security guidance