Kubernetes is one of the most popular open-source containerization tools. Organizations and developers all over the world prefer it over other alternatives as it is cloud-agnostic, efficient, portable, and scalable and offers automated orchestration.
However, the increased sophistication of cyber threats might compel you to rethink the true safety of your Kubernetes environment. Groups like OilRig use custom DNS tunneling protocols to maintain persistent C2 channels, highly effective against Kubernetes clusters. They can send commands and receive data through these DNS queries if your network security overlooks them.
Now that you can recognize the threats looming around your environment, it is time to talk about ways to secure it. The best way, hands down, is Kubernetes vulnerability scanning.
In this post, we will explore Kubernetes vulnerability scanning and how it helps protect against ongoing attacks and threats.
What is Kubernetes Vulnerability Scanning?
Kubernetes Vulnerability Scanning is the method of inspecting for vulnerabilities, such as misconfiguration, improper access, unpatched software, and more. It also helps maintain the security posture of your clusters by identifying and addressing risks. To reduce the chances of exposure to threats, Kubernetes vulnerability scanning checks and ensures that the configurations align with security best practices.
This step-by-step process of investigating for security flaws in your Kubernetes deployment, and rectifying it involves container image and configuration scanning, preferably through an automated tool, followed by updating/adding security patches.
Note that container scanning is complex and is usually not done manually. You can opt for either open-source or paid tools.
What is Kubernetes’ vulnerability?
The weaknesses or flaws within the Kubernetes systems are known as Kubernetes vulnerabilities. Threat actors like hacktivists, cyberterrorists, nation-state hackers, and insider threat actors can exploit these flaws and compromise the integrity, availability, or even confidentiality of the clusters.
While Kubernetes is a powerful tool for managing containerized environments, it is not secure by default because it requires proper configuration, access controls, and regular updates to safeguard it from attacks. In just 5 years, from 2018 to 2023, the number of vulnerabilities in Kubernetes has increased by 440%. Vulnerabilities exist due to misconfigurations, unpatched software, and the complexity of managing distributed environments, which can leave clusters exposed to potential threats that compromise their integrity, availability, and confidentiality.
What is the Impact of Kubernetes vulnerabilities?
Kubernetes vulnerabilities can have serious and wide-ranging effects beyond clusters, compromising the entire security of the organization. Threat actors can access sensitive data and disrupt services by exploiting these weaknesses. They can also use these compromised clusters to expand the attack surface and impact the entire network.
As the container environments are interconnected, one vulnerability can allow attackers to escalate their access and manipulate more resources. This lateral movement increases the scale of damage and makes it more difficult to detect and contain the breach, further emphasizing the need for robust security measures.
In regulated industries, such vulnerabilities can lead to severe legal and financial consequences due to non-compliance with data protection regulations like GDPR or HIPAA. The operational costs of a breach are also significant, involving investigations, service restoration, and reinforcing security measures.
For example, through the CVE-2019-1002101 vulnerability that affected Kubelet, unauthorized users could execute arbitrary commands inside containers, potentially leading to large-scale disruption, data breaches, and operational impact. They did this by exploiting improper input validation within the Kubelet’s API. One such vulnerability can single-handedly disrupt the entire Kubernetes container.
The Importance of Kubernetes Vulnerability Scanning
According to the State of Kubernetes Security Report, 37% of organizations have experienced loss of revenue or customers due to Kubernetes-related security incidents. Moreover, such incidents are not confined to runtime, and can severely impact the full application development cycle. This stands to show how important it is to scan for vulnerabilities.
1. Helps Prevent Data Breaches and Security Incidents.
One of the major reasons to adopt Kubernetes Vulnerability Scanning is that it is mostly automated, no matter how vast your environment is. These scans run on a schedule and offer real-time alerts and responses. You can integrate them with advanced techniques and tools to try and identify new threats and alleviate them. By being on top of the vulnerabilities and threats, you can, ideally, avert and minimize the effect of data breaches and security incidents.
2. Helps Organizations Comply with Regulatory Standards.
When you integrate vulnerability scanning into your workflows, you can ensure compliance with standard industry-specific regulations. For instance, financial companies have to comply with the Payment Card Industry Data Security Standard (PCI DSS), or the healthcare industry has to comply with the Health Insurance Portability and Accountability Act, and telecommunications providers operating across multiple European countries must ensure compliance with the General Data Protection Regulation (GDPR) Result: You avoid the hassle of legal repercussions and hefty fines for non-compliance.
3. Increases the Trust and Reliability of Users and Customers.
Cyber threat actors are not picky when it comes to choosing a target. That is why, for any organization that collects customer data for its operations and uses Kubernetes for containerization, Kubernetes vulnerability scanning is crucial.
Take a look at e-commerce platforms—they collect vital and sensitive customer data. This data can be exploited through security flaws in containers or images. Vulnerability scanning detects these issues and fixes them, avoiding potential data breaches. So now that your end-users know that their data is secured, it gives them a sense of security and also reinforces their trust in the platform/vendor.
4. Helps Identify Vulnerabilities.
Kubernetes Vulnerability Scanning works as an early warning system; it performs regular checks looks for known threats and compares the components and configurations against verified databases such as Common Vulnerabilities and Exposure (CVE) that record all known threats. Some advanced techniques like heuristic analysis and behavioral monitoring can identify anomalies and unusual patterns indicating potential threats.
5. Helps Prioritize Remediation.
Not all vulnerabilities are the same; some can be time-sensitive. Vulnerability scanning offers you visibility into the severity of a vulnerability and its impact on your business. Based on this information, you can decide to prioritize and assign resources to remediate the most critical vulnerabilities. There are several remediation processes such as patch management, rebuilding and redeploying images, and isolating containers. However, Role-Based Access Control or RBAC is most preferred. It is implemented by Policies that define the permissions, and the Subjects – the entities to which these permissions are granted.
6. Helps Organizations in Increasing their Security Posture.
One added advantage of Kubernetes vulnerability scanning is its assistance with zero-day vulnerabilities. Although scanning cannot detect it, with advanced techniques, it can suggest or indicate the emergence of new threats. Well-maintained regularly scanned environments are less susceptible to unknown threats and have better security posture as it reduces the attack surface.
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Read GuideCommon Vulnerabilities in Kubernetes
Since Kubernetes is a relatively complex tool to implement, it is more often than not misconfigured and under-protected from the prying eyes of threat actors. Result: Kubernetes is a prime target for cybercriminals. Here, we will discuss some of the most common vulnerabilities in Kubernetes.
1. Misconfigurations
Misconfiguration vulnerabilities in Kubernetes result from improper RBAC setting, exposed dashboards, and/or weak authentication methods. Any lapse in RBAC settings would mean excessive permission, leading to unauthorized access to sensitive operations. While exposed dashboards with weak or default passwords offer easy entry points into the cluster, misconfigured API opens the door to denial-of-service (DoS) attacks.
2. Inadequate Access Controls
Inadequate access controls simply mean there are no set standards for who can access Kubernetes clusters. Apart from issues with RBAC, there can be weak network policies that allow unrestricted communication between pods, exposing sensitive data to unauthorized users. Pod security policy issues, like improper privilege settings, can also result in unprivileged users gaining excessive control.
3. Unpatched Software
When software vulnerabilities are left unpatched in host operating systems, it can provide attackers with multiple potential entry points or escalation paths. It can affect operating systems, libraries, and other software within a container. If there is unpatched software on the operating system on a Kubernetes node, it could lead to kernel-level exploits like the Dirty COW vulnerability from October 2016. With the highest level of privileges, the attackers can gain control over the entire system.
4. Container Vulnerabilities
Container vulnerabilities refer to the vulnerabilities in the container itself. Outdated images or those from unverified registries may contain vulnerable versions of software like Apache or OpenSSL, increasing the risk of Denial of Service attacks and data breaches. Additionally, containers with excessive privileges can compromise the Kubernetes node, granting attackers access to sensitive host directories. With this access, they can modify system files, potentially impacting other containers on the same node.
The Scanning Process of Kubernetes Vulnerability
The scanning process of Kubernetes Vulnerability involves three significant steps: Static analysis before Kubernetes deployment, during deployment, and post-deployment. Let’s look at these steps in a bit more detail.
Before Deployment: Static Analysis
Static analysis refers to identifying vulnerabilities within the image, such as image source, compliance, and efficiency. The process begins with retrieving the images from either public or private registries. Tools then deconstruct the image’s multiple layers and scrutinize each for vulnerabilities or risky configurations, comparing elements like software packages against databases like the NVD. The analysis checks for configuration risks, like insecure permissions or exposed variables, and ensures compliance with standards such as PCI DSS or HIPAA.
During Deployment: CI/CD Pipelines and Admission Controllers
While deploying the code, it is a good practice to integrate vulnerability scanning practices into CI/CD pipelines. This will ensure that whatever is built is scanned for vulnerabilities automatically. Continuous scanning, which maps with the DevSecOps viewpoint of incorporating security into the development process, enables quick feedback and remediation.
Apart, it is always advisable to configure Kubernetes admission controllers. This helps in preventing the deployment of non-compliant resources and enforcing security policies.
Post-Deployment: Runtime Scanning and Monitoring
To think that work ends after deployment is not correct. Reason: Vulnerabilities can develop over a while. So, it is advisable to continuously scan your running containers and Kubernetes cluster. You can get real-time visibility into the security health of the cluster by using runtime scanning tools to monitor and detect new vulnerabilities and any changes in the security posture.
Understand this: when you monitor the applications’ behaviors and the Kubernetes environment for unusual activity, you can usually detect potential security incidents. You must monitor and look for signs of compromised containers and attempts for unauthorized access amid other security issues.
Top Open-Source Kubernetes Vulnerability Scanners
While there are various open-source vulnerability scanners, here are the top four Kubernetes Vulnerability Scanners for you to assess.
1. Kube-Score
Equipped with an MIT license, Kube-score comprises a web-based user interface (UI) that helps test object definitions. Kube-score performs static code analysis of Kubernetes definitions, checking them against different security controls. The result is the enablement or disablement of controls per your requirements is in your hands. Another crucial advantage of Kube score is its emphasis on human-readable error messages. The messages may include helpful instructions for remediation to help improve security and reliability.
2. Kubeaudit
Developed by Shopify, Kubeaudit has an MIT license and is written in Golang. Kubeaudit helps you audit Kubernetes clusters for various security concerns, such as misconfiguration detection and identifying non-compliance with best practices. Kubeaudit can be easily installed on your local machines using a single command. With Kubeaudit, you also get numerous modes of auditing, including local, cluster, and manifest. Kubeaudit is an easy-to-use open-source vulnerability scanner tool that offers a platform for your community contributions to improve its auditing capabilities.
3. Kube-Bench
An open-source tool, Kube-Bench verifies the secure deployment of Kubernetes. It detects the running version of Kubernetes and aligns it with the corresponding CIS benchmark version. All this is done through default settings. Kube-Bench also tries to identify the components that run on the node and uses them to decide which tests to run. Written in Golang, Kube-Bench’s tests are configured with YAML (Yet Another Markup Language) files. Result: It is easier to update the tool, as per the evolution of test specifications.
4. Kubesec
A risk analysis tool for Kubernetes, Kubesec, is available under open-source license. The tool scans manifest configurations and validates them against predefined security criteria. It can find misconfigurations in deployments or pods. Once the issues are detected, Kubesec assigns a risk score to map these issues with best security practices.
Elements Of Kubernetes Vulnerability Scanning
There are three crucial elements of Kubernetes Vulnerability Scanning and they are: remediating Kubernetes vulnerabilities, scanning container images, and scanning for best practices in Kubernetes configurations.
Remediating Vulnerabilities in Kubernetes
Vulnerabilities within Kubernetes arise from misconfigurations, improper RBAC settings, or unsecured APIs. By identifying these flaws, it’s critical to apply targeted patches or configuration changes to minimize risk. Remediation involves identifying issues and correcting them to prevent exploitation, thus safeguarding the cluster from potential breaches or denial-of-service attacks.
Container Image Scanning
Container images often contain outdated libraries or known vulnerabilities. By systematically scanning these images, we can detect security risks before deployment. This is important because a single vulnerable container can compromise the entire cluster, propagating weaknesses across interconnected services.
Testing for Best Practices in K8 Configurations
Following security best practices guarantees that the cluster operates within secure boundaries. Testing for these practices, including proper RBAC, network isolation, and pod security policies, reduces the risks of unauthorized access or privilege escalation. It’s the application of proactive measures, ensuring the Kubernetes environment remains resilient to potential threats.
Conclusion
Kubernetes, while undeniably one of the most popular open-source container orchestration tools, carries with it a level of complexity that inherently introduces security risks. Its scalability and cloud-agnostic flexibility make it appealing to organizations worldwide, but those very attributes can also make it vulnerable. Now that the cyber threats are increasingly sophisticated and highly targeted, recognizing that Kubernetes is not secure by default is critical.
The need for Kubernetes vulnerability scanning is not optional. It’s a fundamental, proactive defense mechanism that continuously identifies and remediates risks, ensuring compliance with regulatory standards and maintaining user trust.
As you move forward, start by incorporating vulnerability scanning into your CI/CD pipelines, use it to monitor both pre- and post-deployment, and ensure you have automated tools in place to detect and respond to threats in real-time. The sooner you establish these practices, the better your odds of preventing a major incident.
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FAQs
The Kubernetes vulnerability scanning must happen at every stage of the Kubernetes development life cycle. This would guarantee security is a constant focus, right from the initial stages to the final phase of development.
The scan happens in three stages: before deployment, where static analysis happens. Then, during deployment, here the scans are carried out on CI/D pipelines, and then, lastly, post-deployment, continuous scanning and monitoring are essential.
Per the PurpleSec, the usual recommended frequency for you to perform Kubernetes vulnerability scanning is at least once every quarter. However, the frequency may depend on compliance requirements, infrastructure changes, and network security capabilities.
There are several challenges with Kubernetes. Reason: Kubernetes is a complex architecture with all its clusters, nodes, pods, containers, and applications running with it. Lack of centralized vulnerability, infrastructure complexity, networking failures, and cluster instability are some challenges.
Kubernetes’ complexity, resource requirements, security challenges, and continuous maintenance are some of its prominent disadvantages.