CVSS Score Calculator
Calculate cybersecurity vulnerability severity with base, temporal, and environmental metrics
What is CVSS Score?
The Common Vulnerability Scoring System (CVSS) is a free and open industry standard for assessing the severity of computer system security vulnerabilities. CVSS score helps organizations determine the urgency and priority of responding to a security vulnerability by producing a numerical score reflecting the severity of the vulnerability.
CVSS score is used by cybersecurity professionals, IT administrators, and security teams to prioritize patching and remediation efforts. The system provides a way to capture the principal characteristics of a vulnerability and produce a numerical score reflecting its severity.
A common misconception about CVSS score is that it represents the actual risk to an organization. However, CVSS score measures the inherent characteristics of a vulnerability, not the likelihood that the vulnerability will be exploited or the business impact of such exploitation.
CVSS Score Formula and Mathematical Explanation
The CVSS score calculation involves multiple components including base metrics, temporal metrics, and environmental metrics. The base score formula is:
Base Score = (Impact + Exploitability) × F(Impact)
Where Impact is calculated differently based on the Scope metric. For unchanged scope: Impact = 1 – [(1 – C) × (1 – I) × (1 – A)]. For changed scope: Impact = (1 – (1 – C) × (1 – I) × (1 – A)) × 1.08.
| Metric | Description | Possible Values | Impact on Score |
|---|---|---|---|
| Attack Vector (AV) | How the vulnerability is exploited | N/A/L/P | Network (0.85) – Physical (0.2) |
| Attack Complexity (AC) | Conditions beyond attacker’s control | L/H | Low (0.77) – High (0.44) |
| Privileges Required (PR) | Level of privileges required | N/L/H | None (0.85) – High (0.27) |
| User Interaction (UI) | Human interaction required | N/R | None (0.85) – Required (0.62) |
| Scope (S) | Does vulnerability affect other resources | U/C | Unchanged (0.0) – Changed (1.0) |
Practical Examples (Real-World Use Cases)
Example 1: Remote Code Execution Vulnerability
Consider a vulnerability in a web server that allows remote code execution without authentication. The metrics might be: AV:N (Network), AC:L (Low), PR:N (None), UI:N (None), S:C (Changed), C:H (High), I:H (High), A:H (High).
Using our CVSS score calculator, this would result in a base score of approximately 9.8, which falls into the Critical severity category. This indicates a highly severe vulnerability that requires immediate attention and patching.
Example 2: Local Privilege Escalation
A local privilege escalation vulnerability where an authenticated user can gain higher privileges might have these metrics: AV:L (Local), AC:H (High), PR:L (Low), UI:N (None), S:U (Unchanged), C:H (High), I:H (High), A:H (High).
This configuration would result in a base score of approximately 7.0, falling into the High severity category. While serious, this vulnerability is less urgent than the remote code execution example since it requires local access.
How to Use This CVSS Score Calculator
Using our CVSS score calculator is straightforward. First, identify the appropriate values for each of the base metrics based on the vulnerability you’re analyzing. Select the corresponding options from each dropdown menu.
- Determine the Attack Vector based on how the vulnerability can be exploited
- Select the Attack Complexity considering conditions beyond the attacker’s control
- Choose the required Privileges level needed to exploit the vulnerability
- Indicate whether User Interaction is required to exploit the vulnerability
- Determine if the Scope changes when the vulnerability is exploited
- Select the impact levels for Confidentiality, Integrity, and Availability
Once all metrics are selected, click “Calculate CVSS Score” to see the results. The calculator will automatically update the scores as you make selections. The primary result shows the base CVSS score and its associated severity rating.
When interpreting results, remember that CVSS scores range from 0.0 to 10.0. Scores of 0.1-3.9 are Low severity, 4.0-6.9 are Medium, 7.0-8.9 are High, and 9.0-10.0 are Critical. Use these ratings to prioritize your security response activities.
Key Factors That Affect CVSS Score Results
Several critical factors influence the final CVSS score, making it essential to understand each component:
- Attack Vector (AV): Network-based attacks receive higher scores than local or physical access requirements. Remote exploitable vulnerabilities are more dangerous because they don’t require physical presence or prior system access.
- Attack Complexity (AC): Lower complexity increases the score since it means fewer conditions need to be met for exploitation. Complex attacks requiring specific configurations receive lower scores.
- Privileges Required (PR): Vulnerabilities requiring no privileges receive higher scores than those requiring low or high privileges. The more access required, the lower the score.
- User Interaction (UI): Vulnerabilities requiring no user interaction are scored higher than those requiring user action. Social engineering dependencies reduce the score.
- Scope Change (S): When exploitation affects resources beyond the vulnerable component, the score increases significantly. This reflects broader potential damage.
- Impact Metrics (CIA): Higher impacts on Confidentiality, Integrity, and Availability increase the score. Complete loss of these attributes results in maximum impact values.
- Exploitability vs. Impact Balance: The formula balances exploitability (how easy it is to exploit) with impact (what happens when exploited). Both factors are equally important.
Frequently Asked Questions (FAQ)
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