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Understanding Vulnerability Scoring to Help Measure Risk
Understanding Vulnerability Scoring to Help Measure Risk

by Matthew Jerzewski on March 13, 2019

Understanding vulnerability scoring can be a daunting task, but a good starting point is first understanding risk and being able to distinguish risk from a vulnerability. Both have been used interchangeably throughout the years.

A vulnerability is some aspect of a systems functioning, configuration or architecture that makes the resource a target of potential misuse, exploitation or denial of service.

Risk, on the other hand, is the potential that the threat will be realized for a particular vulnerability.

There are many methods available for ranking vulnerabilities to determine their level of associated risk. The Common Vulnerability Scoring System (CVSS) is the most widely used industry standard for this purpose. There are three versions of CVSS, CVSSv1, CVSSv2 and CVSSv3. CVSSv1 was in 2005, followed by CVSSv2 in 2007 and the current version, CVSSv3, in 2015.

To get a better understanding of CVSS, we need to see how the scoring system has evolved.

CVSSv1 was designed to rank information system vulnerabilities and provide the end user with a composite score representing the overall severity and risk the vulnerability presents. CVSS uses a modular system structure with three groups: Base Metric Group, Temporal Metric Group and Environmental Metric Group. These three groups create three separate formulas that combine to create an overall vulnerability score between 0 and 10, with 10 being most severe.

The Base Metric Group is where the foundation of the vulnerability scoring will be handled. This includes attack vectors, integrity impact, impact bias, access complexity, confidentiality impact, availability impact and authentication requirements. These core characteristics will not change over time, nor will they change if a different target environment is added.