In the modern world, where almost all apps and software are cloud-based, Kubernetes remains the central container management platform for developers. Kubernetes usually allows for the development, deployment, and management of microservices in a scalable and flexible manner. The platform works with cloud service providers, runtime interfaces for containers, authentication providers, and extensible integration points for effective management.

It is, however, essential to point out that Kubernetes has one major vulnerability – the possibility of security breaches. Furthermore, given that the platform uses an integrator approach when running containerized applications on any infrastructure platform, it is hard to develop a holistic security structure around Kubernetes and stacked applications.

According to the security report “State of Kubernetes,” released by Red Hat in 2022, many management platform users had their deliveries halted due to unaddressed security concerns. Additionally, within the preceding 12 months, almost every management platform user experienced at least one security breach incident. Based on this information, it is safe to deduce that Kubernetes environments are not entirely secure by default and are open to occasional breaches.

In this article, the focus will be on discussing the top 10 Kubernetes security risks, real-life and relatable examples of how the risks can occur, and top tips on shoring up security and preventing the occurrence of the risks mentioned.

Top 10 Potential Kubernetes Vulnerabilities

1. Kubernetes Secrets

Secrets form the core of how Kubernetes environments store sensitive information like passwords, tokens, or certificates and how they are used inside application containers. 

Three crucial issues come to the fore when dealing with Kubernetes secrets:

a.) Secrets contain sensitive information in base-64 encoded strings, but these are not encrypted by default. Though Kubernetes offers encryption for storing data, you must first configure the platform to do this automatically. The biggest threat to secrets is that whenever a user accesses a pod, they and any other applications running inside the pod using the same namespace can access and read the secrets.

b.) Role-Based Access Control (RBAC) allows you to control who gets access or control over Kubernetes resources. However, you must first properly configure your RBAC rules to allow only relevant applications and persons to access the secrets.

c.) ConfigMaps and Secrets are the two methods you can use to pass data to running containers. However, note that any unused secrets and ConfigMap resources within the containers can lead to confusion and increase the risk of secure data being breached. For example, if you delete the application used to convey data and forget to clear the secret(s), then any malicious pod with access to your passwords can use them in the future.

2. Possibility of Container Images with Security Vulnerabilities

Kubernetes allows for the orchestration, distribution, and running of separate containers on worker nodes. However, the platform does not check individual containers for potential and actual security breaches.

Therefore, it is imperative to scan container images before deploying them to worker nodes to ensure that only container images from trusted registries with no potentially devastating kubernetes vulnerabilities (for example, remote code execution) run on the cluster. Furthermore, the scanning of container images should be integrated into CI/CD systems to allow for automation and quick detection of potential breaches.

3. Potential of Runtime Threats

Some Kubernetes workloads (specific containers) run on worker nodes, with the individual container being controlled by the host operating system of the infrastructure at the node in runtime. Therefore, if any container images have a vulnerability or if there are any enabled access permissions, they can open a backdoor into your entire cluster. It is, therefore, imperative to have an OS-level runtime protection feature. Note that the best protection you can get for Kubernetes vulnerabilities and runtime threats is to enact the ‘least-privileged principle’ throughout the Kubernetes environment.

Some open-source tools, such as AppArmor, Seccomp, and SELinux, are widely accepted at the Linux kernel level that you can use to restrict access and implement your desired security policies. It is, however, important to note that these tools are not found by default in the Kubernetes environment. As such, you need to configure them externally to get protection against runtime threats. If you want automated runtime protection, consider trying the Kubernetes Security Posture Management (KSPM) approach. This approach relies on a host of automation tools to help holistically detect, alert security, and fix configuration and compliance issues.

4. The Default Kubernetes Settings and Potential Cluster Misconfigurations

The API from Kubernetes usually consists of a host of complex configuration options and resource definitions. This means that the platform comes with default values for most of its configurations to remove the burden of crafting long YAML files from the user.

However, it is important to note three critical issues that arise when it comes to cluster configurations and deployment of resources.

a.) The default configurations in the Kubernetes environment are significant as they help increase agility and flexibility when containers are running, but they are not the most secure options available

b.) Online examples of Kubernetes resources are helpful to get you started on development, but it is imperative to ascertain what the resources you allocate will deploy to your clusters

c.) It is not unusual to change the allocation of Kubernetes resources using the “kubectl edit” commands when creating your clusters. If you forget to update the changes you make on the source file, they will be overwritten once you deploy resources next time. These untracked modifications to the source file can lead to unpredictable behavior

5. The RBAC Policies in Kubernetes

Kubernetes employs RBAC policies to manage and control authorization over resources. It is, therefore, essential to configure and maintain RBAC policies in your Kubernetes environment to prevent unwanted access to resources.

You should remember two main things when working on RBAC policies for your Kubernetes environment…

a.) Some policies, such as the role of having a cluster_admin(s), are too permissive as they allow the user to do anything they want in a cluster. This role is typically assigned to regular developers to improve their agility. The downside is that attackers will quickly get high-level access using the cluster_admin’s node in case of a breach. To avoid this, consider configuring your RBAC policies to align specific resources for specified user groups

b.) various variable environments arise in the software development cycle, such as development, testing, staging, and production. Each of these environments requires different resources. As such, ensure that you configure your RBAC policies to align with the needs of each group. This will also help prevent exposure

6. Network Policies

In the Kubernetes environment, one terminal can connect to other nodes, even those with external addresses. Other nodes inside each cluster can access this terminal by default. Kubernetes has in-built network policies designed to manage and even restrict the access of networks between namespaces, IP blocks, and separate terminals.

Note that in some instances, network policies can collude with the labels on the terminals meaning that some terminals get unwarranted access. When clusters are held in clouds, you should ensure that the cluster network is isolated from the rest of the Virtual Private Cloud (VPC).

8. Potential Vulnerabilities in the Kubernetes API

The Kubernetes API is the core of the entire environment. Here internal and external clients can communicate with and within this management system. However, suppose you are going to use the API in-house. In that case, it is essential to exercise caution since the server and its constituent components are based on open-source tools that have potential (and actual) security vulnerabilities. To counter this issue, you should run the latest stable version of Kubernetes and patch any live clusters you deploy as quickly as possible.

If you are operating in a cloud environment, control of the Kubernetes environment will be in the hands of the cloud provider, meaning that patches and updates happen automatically. However, in most cases, users are responsible for personally upgrading worker nodes. You can rely on resource allocation and automation tools to upgrade or replace your nodes.

9. Potential for Excessive Resource Requests and Resource Limits

Apart from deploying and running containers, Kubernetes can also limit the usage of resources in terms of memory and CPU. Though Kubernetes mostly ignores this, the number of requests and available limits are essential for two important reasons:

a.) Security – If the terminals and namespaces are not restricted, then one container with a security breach can access sensitive data inside your entire cluster

b.) Cost – When the number of requested resources is more than what is being used, the worker nodes will run out of available resources. In addition, when automatic scaling is enabled, this will lead to more node pools which will inevitably increase your cloud bill.

When the resource requests are correctly calculated and assigned, the entire cluster works more efficiently in terms of processing power and memory. Additionally, when you set limits on the number of available resources, faulty applications and intruders in your clusters will automatically find that there are limited resources. This is important since, for example, if you have limitless resources, then a malicious container can consume all the available resources in the node and render the purpose of your application pointless.

10. Data Collection, Deployment, and Storage.

Although the containers in a Kubernetes environment are designed to be fleeting, the API makes it possible to deploy Stateful containerized applications in a way that is both scalable and reliable. For example, with the StatefulSet resources, you can quickly employ data analytic tools, databases, and other machine learning applications in the Kubernetes environment. The data will be accessible to the terminals as volumes attached to the containers.

However, it is crucial to limit access to cluster resources through labels and policies to prevent other terminals in the cluster from getting unwarranted access. Additionally, it is essential to remember that storage in the Kubernetes environment is managed by external systems hence the need to consider encrypting vital data within the cluster. Finally, if you manage your storage plugins, it is also important to check if the security parameters for data access are enabled.

Final Word

Kubernetes takes the award for being the premier container management platform through which you can run microservice applications. However, ensuring holistic security across the entire platform remains challenging, as this is not the project’s key focus. You, therefore, need to go the extra mile to make the security of your clusters and applications more formidable.