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Container Vulnerability Scanning: An In-Depth Guide

Updated on: December 1, 2022

Container Vulnerability Scanning: An In-Depth Guide

The rise of container technology has been an exciting change in the security landscape. Containers are an essential step forward in modernizing how applications are developed, deployed, and run. However, with the benefits of containers also comes the responsibility of securing them in production environments. 

This blog will help IT professionals understand what container vulnerability scanning is, why they should be scanning container technology, how to do it, and the most critical question, how they know they are running a secure environment.

What are Containers, and Why is everyone using them?

Containers are lightweight, stand-alone, executable packages that include everything needed to run the application: code, runtime, system tools, system libraries, settings.

In the past, applications were installed natively on the operating system. Containers, however, provide an isolated environment for applications to run in. The application is installed within a container, including a specific operating system, libraries, and executable files. 

When the container is started, the application runs on the operating system in that isolated environment. Containers are easy to deploy and start. They are independent and can run on their own. This makes them portable to many different environments and easy to integrate into existing applications.

Before diving into container vulnerability scanning, let’s look at what Vulnerability Scanning is?

Introduction to Vulnerability Scanning

Vulnerability scanning is finding security vulnerabilities in the applications (web, mobile, network, blockchain) using manual or automated scanners. Vulnerability scanning is a crucial part of any security program. It allows security personnel to keep track of known vulnerabilities, prioritize them, and plan the best way to fix them.

The vulnerability scanning process includes data collection, analysis, categorization, prioritization, and reporting of vulnerabilities. Manual vulnerability scanning is increasingly being replaced with automated vulnerability scanning. Automatic vulnerability scanning is performed on a website or software using an automated vulnerability scanner. 

Automated vulnerability scanning is more cost-effective and scalable than manual vulnerability scanning. Automatic vulnerability scanning is being used by organizations to test for security vulnerabilities.

What is Container Vulnerability Scanning?

Container Vulnerability Scanning is a technique that can check for known vulnerabilities in the containers that make up your application. It is a way to check if you are exposed to risks that could be exploited. 

You can think of Container Vulnerability Scanning as the equivalent of running a vulnerability scan on your operating system to check if you have any unpatched vulnerabilities. The most common use case for container vulnerability scanning is to check if the container images you use in your application have any known vulnerabilities. 

Why is Container Security complex?

Container Vulnerability Scanning has become more and more popular in recent years. That is because Docker has grown in popularity, and the process has become more and more complex. A lot of software is built on top of Docker, and the container ecosystem has grown significantly, which means there are many more components that need to be checked for vulnerabilities. 

Since the advent of microservices, the container ecosystem has become more complex. The more components you add to your application, the more complex the process of checking for vulnerabilities becomes.

The complexity of containers makes it a more difficult target for developers and security researchers. The challenge is that containers are a new technology and container security is relatively new. Many of the best practices have not been defined yet.

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Top 3 Container Level Vulnerabilities

Container technologies such as Docker are often considered to be safe and reliable. However, the reality is that they are vulnerable to several issues concerning security. The only way to eliminate the risk is to avoid containers altogether. When it comes to container-level vulnerabilities, the most common are: 

1. Escape vulnerabilities

This vulnerability is caused by code that allows execution from user input. The vulnerability can be used to escape the container by using a command that the user provides. 

For example, the user can provide the command cat /etc/passwd and the vulnerability will escape the container.

2. Attribute disclosure 

This vulnerability is caused by a lack of restriction on the environment variables that the container can access and manipulate. This vulnerability can be used to obtain information that should not be available to the container. 

For example, the container should not manipulate the host’s network interfaces, but the vulnerability allows the container to do so. 

3. Known Vulnerabilities in Components

One of the most common ways to exploit vulnerabilities in the Docker daemon is to get a root shell, which allows the attacker to read any file on the server and execute any command as root. One way to compromise the Docker daemon is to exploit a vulnerability in a library that is used by one of the many Docker tools (e.g., docker-cli-js). 

How to discover container vulnerabilities during the SDLC pipeline?

Container images are the deliverable artifacts of a software project. Security vulnerabilities must be detected in the source code and the container images. Modern software development life cycle (SDLC) offers an opportunity to check container images for security vulnerabilities known as container vulnerability scanning.

In the past, the image vulnerability scanning was only conducted at the time of image build (or build time). However, this process is not comprehensive enough as it doesn’t cover the time when the image is being used in production. 

The approach mentioned above does not also cover the vulnerabilities introduced at image build. It is essential to scan images simultaneously as code is scanned (during code review) for potential security issues. This scanning can be manual or automated based on the organization’s decision.

10 Best Practices to avoid Container Vulnerabilities

The hype around containers has been growing over the past years, and with good reason. Containers allow you to run multiple applications in isolated environments on a single machine, or even in the cloud, without worrying about conflicting resources or configuration issues. 

The use of containers is now considered a best practice, especially in terms of speed and flexibility. However, just like any new technology, containers are not immune to security issues. As with any new technology, it is essential to follow best practices to avoid common security concerns, such as:

1. Assign unique UIDs and GIDs to each container.

2. Limit and control user IDs, groups, and capabilities. 

3. Enable mandatory access control. 

4. Do not share host directories with containers.

5. Disable container login by default. 

6. Use seccomp for filtering system calls. 

7. Avoid using root user

8. Perform regular container vulnerability scanning 

9. Disable container capabilities. 

10. Use security-enhanced Linux for fine-grained controls.

Although the list is never-ending but the above mentioned are must haves.

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Top 5 Open Source Container Vulnerability Scanning Tools

Container vulnerability scanning is increasingly becoming a must-have for organizations looking to secure the applications running in their infrastructure. However, vulnerability scanning containers is still a relatively new concept. Thus, only a few excellent open-source container vulnerability scanning tools are available. 

1. Clair: Clair is one of the most used open-source container vulnerability scannings that offers a static analysis of vulnerabilities in application containers. Vendors use it for vulnerability detection and users for vulnerability analysis.

2. Grype: Grype is an easy-to-use and straightforward container vulnerability scanner. It is designed to quickly scan containers and filesystems for common vulnerabilities in the most popular CVE database. Grype is powered by Syft, the open-source software bill of materials (SBOM) tool for container images and filesystems.

3. Docker Bench for Security: Docker Bench for Security, commonly abbreviated as DBFS, is a script to audit Docker containers against security benchmarks. DBFS is best described as a security benchmarking tool, which checks for standard best practices around deploying Docker containers in production environments. DBFS has been developed by the Sysdig team in collaboration with the SANS Institute, the University of New Haven, and many other awesome folks.

4. Trivy: Trivy is a security scanner for container images. It allows you to scan images for vulnerabilities and configuration issues before using them. The goal is to help you verify your containers’ security and detect configuration issues or vulnerabilities before you deploy your application. Trivy is an entirely open-source project with its source code hosted on Github.

Why Choose Astra Security for Container Vulnerability Scanning?

Astra Security is one of the leading Cyber Security companies in India. At Astra, we provide a wide range of Cyber Security services, including Container Vulnerability Scanning, Web Application Security, Network Penetration Testing, Penetration Testing, and CMS Protection. 

With over a decade of experience and a team of top professionals in the industry, Astra ensures that its services are delivered with the highest standards in quality, reliability, and professionalism. Astra’s experts are capable of meeting the most demanding requirements and providing highly advanced security services and solutions.

Why Choose Astra for Container Vulnerability Scanning?
Image: Why Choose Astra for Container Vulnerability Scanning?


Hopefully, this guide has provided you with all the information you need to understand better container vulnerability scanning and the different tools you can use to help keep your containers safe. If you want to learn more about how we can help you with container vulnerability scanning, feel free to contact us anytime. Thank you for reading. We are always excited when one of our posts can provide helpful information on this topic!

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Jinson Varghese

Jinson Varghese Behanan is an Information Security Analyst at Astra. Passionate about Cybersecurity from a young age, Jinson completed his Bachelor's degree in Computer Security from Northumbria University. When he isn’t glued to a computer screen, he spends his time reading InfoSec materials, playing basketball, learning French and traveling. You can follow him on Medium or visit his Website for more stories about the various Security Audits he does and the crazy vulnerabilities he finds.

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