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What is CVSS Score?

Discover what a CVSS Score is and how it helps prioritize software vulnerability fixes using a 0-10 scale. Learn about its metrics and real-world application.

Explain Like I'm 5

Think of the CVSS Score like a safety rating for software. Imagine you're checking how secure different houses are. Some have strong locks, some have alarms, and others might have open windows. You'd rate each house based on how easy it is to break in. The CVSS Score does this for software, giving each security flaw a score from 0 to 10 based on how risky it is.

Just like you'd fix the most vulnerable houses first, cybersecurity teams use CVSS Scores to know which software problems to tackle first. A score of 0 means the software is very secure, like a house with a moat. A score of 10 means it's wide open, like a door left ajar. Knowing these scores helps keep computer systems safe from hackers.

Technical Definition

Definition

The Common Vulnerability Scoring System (CVSS) Score is a standardized method for evaluating the severity of security vulnerabilities in software. It assigns a numerical score from 0 to 10, with higher scores indicating more severe vulnerabilities.

How It Works

  1. 1Base Metrics: These capture the inherent qualities of a vulnerability, such as its impact and how easily it can be exploited.
  2. 2Temporal Metrics: These adjust the base score based on factors that change over time, like the availability of exploits or patches.
  3. 3Environmental Metrics: These modify the score based on the specific environment, considering the importance of affected IT assets.
  4. 4Severity Ratings: CVSS scores translate into severity ratings: None (0.0), Low (0.1-3.9), Medium (4.0-6.9), High (7.0-8.9), and Critical (9.0-10.0).

Key Characteristics

  • Scalable: Applicable to any vulnerability across systems.
  • Structured: Uses three metric groups (Base, Temporal, Environmental) for thorough assessment.
  • Version Updates: CVSS v3.1 offers refined metrics compared to v2.

Comparison

AspectCVSS v2CVSS v3.1
Metric GroupsBase, Temporal, EnvironmentalBase, Temporal, Environmental
Scoring PrecisionLess granularMore granular
Severity RatingsLess nuancedMore nuanced

Real-World Example

CVE-2021-44228, known as Log4Shell, received a CVSS v3.1 score of 10.0, highlighting its critical nature due to easy exploitation and severe impact on confidentiality, integrity, and availability.

Detection & Prevention

  • Tools: Utilize nmap, Burp Suite, and OWASP ZAP to detect vulnerabilities.
  • Patching: Prioritize patches based on CVSS scores.
  • Environment Assessment: Regularly assess environmental changes affecting vulnerability severity.

Common Misconceptions

  • Myth 1: "A high CVSS score means immediate exploitation." Not all high-scoring vulnerabilities are actively exploited.
  • Myth 2: "CVSS scores are static." Scores can change with new information or environmental changes.
  • Myth 3: "CVSS scores alone dictate patching priorities." Business impact and asset value should also be considered.

Keywords

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