Ensure there is no unrestricted inbound access to TCP port 10257 (kube-controller-manager)

Security & Compliance
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TCP port 10257 is used by the kube-controller-manager component of Kubernetes, which is responsible for maintaining the desired state of the cluster by controlling various controllers that handle different aspects of the system, such as deployments, services, and replicas. The kube-controller-manager communicates with the Kubernetes API server to obtain information about the cluster's current state and make decisions based on that information. To ensure the security of a Kubernetes cluster, it is important to restrict access to TCP port 10257 to only authorized users and systems. Unrestricted inbound access to this port can potentially allow attackers to read or modify critical control data, execute arbitrary code, and even gain control of the kube-controller-manager and affect the overall availability of the cluster.‍


Here are the remediation steps to ensure there is no unrestricted inbound access to TCP port 10257 (kube-controller-manager):

  1. Identify all systems that require access to the kube-controller-manager through TCP port 10257.
  2. Implement firewall rules and access control lists (ACLs) to block all incoming traffic to port 10257, except for authorized hosts or IP addresses that require access to the kube-controller-manager.
  3. Use a network security group (NSG) to filter traffic to the Kubernetes cluster's network interface, and configure it to only allow traffic from authorized sources.
  4. Enable Transport Layer Security (TLS) encryption for all communication to and from the kube-controller-manager to protect against eavesdropping and man-in-the-middle attacks.
  5. Regularly monitor the network traffic to the Kubernetes cluster to detect any unauthorized attempts to access the TCP port 10257.
  6. Regularly review and update the firewall rules, access control lists, and network security groups to ensure they are up to date and configured correctly.

By following these remediation steps, you can ensure that the Kubernetes cluster is secured and that access to the TCP port 10257 is restricted only to authorized sources, reducing the risk of unauthorized access, data loss, and other security incidents.

Enforced Resources
Note: Remediation steps provided by Lightlytics are meant to be suggestions and guidelines only. It is crucial to thoroughly verify and test any remediation steps before applying them to production environments. Each organization's infrastructure and security needs may differ, and blindly applying suggested remediation steps without proper testing could potentially cause unforeseen issues or vulnerabilities. Therefore, it is strongly recommended that you validate and customize any remediation steps to meet your organization's specific requirements and ensure that they align with your security policies and best practices.