Kubernetes Security: Common Vulnerabilities, Exposures, and Best Practices

Container Security Issues

Kubernetes has become the de‑facto tool for orchestrating, scaling, automatically deploying, and managing containerized applications, but its widespread adoption brings significant security concerns that must be continuously addressed.

Human‑defined rules for how applications run and interact can introduce defects; even minor mistakes by administrators can compromise an entire cluster, as illustrated by high‑profile vulnerabilities such as Log4j.

Software can never be 100 % secure, so ongoing vulnerability discovery, assessment, and patching are essential to protect clusters from exploitation.

Configuration Dilemmas

New Kubernetes users often struggle with security configuration because the platform provides few secure defaults, leaving critical settings like network policies and RBAC to be manually defined.

Enabling Role‑Based Access Control (RBAC) and carefully setting attributes such as allowPrivilegeEscalation and readOnly can greatly improve security posture.

{
    "apiVersion": "abac.authorization.kubernetes.io/v1beta1",
    "kind": "Policy",
    "spec": {
        "user": "bob",
        "namespace": "projectCaribou",
        "resource": "pods",
        "readonly": true
    }
}

In this example, user "bob" is granted read‑only access to pods in the projectCaribou namespace; any write or update request would be denied.

Malicious Code in Docker Images

Because Kubernetes primarily runs Docker images, attackers often target vulnerabilities within those images to gain footholds on the cluster or nodes.

Mitigations include limiting memory usage to prevent DoS attacks, configuring ingress controllers to rate‑limit requests, applying IP‑based access control lists, and scanning images for malicious code before deployment.

Cluster Security and Insecure Transport

While cluster‑level security is often prioritized, the transport layer is frequently overlooked; by default, inter‑service communication lacks encryption, exposing traffic to eavesdropping.

Enabling TLS for service‑to‑service traffic—using solutions like Linkerd that provide automatic TLS and telemetry—protects both the control plane and data plane, including the etcd datastore.

Runtime Security

Even after hardening configuration and policies, runtime threats persist, such as compromised containers running malicious processes or cryptocurrency miners.

Monitoring runtime activity (processes, network connections) and correlating build‑time metadata with observed behavior helps detect anomalies early.

Compliance Issues

Meeting security standards, regulatory requirements, and internal policies in cloud‑native environments can be challenging, especially when security is neglected during container adoption.

Embedding security controls early in the container lifecycle and automating compliance checks reduces operational overhead and risk.

Conclusion

Security is a fundamental concern for containers and Kubernetes; the goal is to make unauthorized access difficult and to ensure that, if a breach occurs, the infrastructure can detect abnormal activity and respond effectively.

Translated from “Kubernetes Security – Common Vulnerabilities and Exposures for K8s Programs” by Prajwal Kulkarni.