This document explains the security levels for advisories that we post on our Security page.
As of TSR-2015-0001, we use the Common Vulnerability Scoring System version 2 (CVSSv2) to score vulnerabilities. When we disclose a vulnerability, we provide the vulnerability's CVSSv2 Base Score and its Base Vector. You can use the CVSSv2 Base Vector to determine the complete CVSSv2 score.
Base Score and Base Metrics
The Base Score is a numeric value that ranges from
10, and increases as vulnerability levels increase. A value of
10 indicates the most severe vulnerabilities. The Base Metrics are vulnerability characteristics that remain constant regardless of changes in time or user environments.
To calculate the Base Score, assign values to the Base Metrics. For information about how to calculate base scores, visit
first.org's A Complete Guide to the CVSSv2 documentation.
The Base Vector describes the components from which the Base Score is calculated. Base Vectors display in the following structure:
You must choose one option for each set of brackets.
- Metrics that the brackets do not contain are mandatory, and you must include them to create a valid CVSS vector.
- Each letter or pair of letters represents a metric or metric value within CVSS.
The table below defines each Base Vector metric and their possible values:
|A vulnerability's network exploit level.|
|A vulnerability's required attack complexity.|
|A vulnerability's required account authentication level.|
|A vulnerability's information confidentiality impact.|
|A vulnerability's account integrity impact.|
|A vulnerability's account availability impact.|
Legacy Security Levels
For information about security levels prior to TSR-2015-0001, read our Legacy Security Levels documentation.