Vulnerabilities 101

A vulnerability in cybersecurity is defined as a weakness or flaw in the design, implementation or behaviours of a system or application. An attacker can exploit these weaknesses to gain access to unauthorised information or perform unauthorised actions. The term “vulnerability” has many definitions by cybersecurity bodies. However, there is minimal variation between them all.

For example, NIST defines a vulnerability as “weakness in an information system, system security procedures, internal controls, or implementation that could be exploited or triggered by a threat source”.

Vulnerabilities can originate from many factors, including a poor design of an application or an oversight of the intended actions from a user.

We will come on to discuss the various types of vulnerabilities in a later room. However, for now, we should know that there are arguably five main categories of vulnerabilities:

As a cybersecurity researcher, you will be assessing applications and systems - using vulnerabilities against these targets in day-to-day life, so it is crucial to become familiar with this discovery and exploitation process.

It is arguably impossible to patch and remedy every single vulnerability in a network or computer system and sometimes a waste of resources.

After all, only approximately 2% of vulnerabilities only ever end up being exploited (Kenna security., 2020). Instead, it is all about addressing the most dangerous vulnerabilities and reducing the likelihood of an attack vector being used to exploit a system.

This is where vulnerability scoring comes into play. Vulnerability scoring serves a vital role in vulnerability management and is used to determine the potential risk and impact a vulnerability may have on a network or computer system. For example, the popular Common Vulnerability Scoring System (CVSS) awards points to a vulnerability based upon its features, availability, and reproducibility.

Of course, as always in the world of IT, there is never just one framework or proposed idea. Let’s explore two of the more common frameworks and analyse how they differ.

Common Vulnerability Scoring System

First introduced in 2005, the Common Vulnerability Scoring System (or CVSS) is a very popular framework for vulnerability scoring and has three major iterations. As it stands, the current version is CVSSv3.1 (with version 4.0 currently in draft) a score is essentially determined by some of the following factors (but many more):

  1. How easy is it to exploit the vulnerability?

  2. Do exploits exist for this?

In fact, there are so many variables that you have to use a calculator to figure out the score using this framework. A vulnerability is given a classification (out of five) depending on the score that is has been assigned. I have put the Qualitative Severity Rating Scale and their score ranges into the table below. 

However, CVSS is not a magic bullet. Let's analyse some of the advantages and disadvantages of CVSS in the table below:

Vulnerability Priority Rating (VPR)

The VPR framework is a much more modern framework in vulnerability management - developed by Tenable, an industry solutions provider for vulnerability management. This framework is considered to be risk-driven; meaning that vulnerabilities are given a score with a heavy focus on the risk a vulnerability poses to the organisation itself, rather than factors such as impact (like with CVSS).

Unlike CVSS, VPR scoring takes into account the relevancy of a vulnerability. For example, no risk is considered regarding a vulnerability if that vulnerability does not apply to the organisation (i.e. they do not use the software that is vulnerable). VPR is also considerably dynamic in its scoring, where the risk that a vulnerability may pose can change almost daily as it ages.

VPR uses a similar scoring range as CVSS, which I have also put into the table below. However, two notable differences are that VPR does not have a "None/Informational" category, and because VPR uses a different scoring method, the same vulnerability will have a different score using VPR than when using CVSS.

Throughout your journey in cybersecurity, you will often come across a magnitude of different applications and services. For example, a CMS whilst they all have the same purpose, often have very different designs and behaviours (and, in turn, potentially different vulnerabilities).

Thankfully for us, there are resources on the internet that keep track of vulnerabilities for all sorts of software, operating systems and more! This room will showcase two databases that we can use to look up existing vulnerabilities for applications discovered in our infosec journey, specifically the following websites:

1. NVD (National Vulnerability Database)

2. Exploit-DB

Before we dive into these two resources, let's ensure that our understanding of some fundamental key terms is on the same page:

NVD – National Vulnerability Database

The National Vulnerability Database is a website that lists all publically categorised vulnerabilities. In cybersecurity, vulnerabilities are classified under “Common Vulnerabilities and Exposures” (Or CVE for short).

These CVEs have the formatting of CVE-YEAR-IDNUMBER. For example, the vulnerability that the famous malware WannaCry used was CVE-2017-0144.

NVD allows you to see all the CVEs that have been confirmed, using filters by category and month of submission. For example, it is three days into August; there have already been 223 new CVEs submitted to this database.

While this website helps keep track of new vulnerabilities, it is not great when searching for vulnerabilities for a specific application or scenario.

Exploit-DB

Exploit-DB is a resource that we, as hackers, will find much more helpful during an assessment. Exploit-DB retains exploits for software and applications stored under the name, author and version of the software or application.

We can use Exploit-DB to look for snippets of code (known as Proof of Concepts) that are used to exploit a specific vulnerability.

Nice work! We’ve made it to the end. This room has served as an introductory to vulnerability research and some skills and resources this requires, where you have practically applied this knowledge.