Executive Summary

A critical vulnerability has been disclosed in the Ingress-NGINX controller, one of the most popular solutions for managing external access to services in a Kubernetes cluster. The flaw can be exploited by an attacker to achieve arbitrary code execution (RCE) on the ingress controller pod itself. Because the ingress controller is a privileged component that handles and routes all incoming traffic, its compromise has severe security implications. An attacker could intercept sensitive data, manipulate traffic, and, most dangerously, use the compromised ingress pod as a staging point to attack other services within the cluster. Administrators of Kubernetes clusters using Ingress-NGINX must treat this as a high-priority threat and apply available patches or mitigations immediately.

Vulnerability Details

The source article does not provide a CVE ID or specific technical details of the vulnerability. However, based on the description, the flaw likely resides in how the ingress controller parses configuration snippets or annotations within an Ingress object. A malicious user with permissions to create or modify Ingress objects could potentially craft a payload that, when processed by the controller, leads to command injection or another form of code execution within the NGINX pod.

This is a form of T1190 - Exploit Public-Facing Application, but with the added context of a cloud-native environment, where it can also lead to T1610 - Deploy Container or other container escape techniques.

Affected Systems

All Kubernetes clusters that use a vulnerable version of the community-supported Ingress-NGINX controller are affected. It is crucial to distinguish this from the F5-supported NGINX Ingress Controller, which is a different product.

Exploitation Status

The articles do not specify if the vulnerability is being actively exploited. However, given its criticality and the widespread use of Ingress-NGINX, it is highly likely that proof-of-concept exploits will be developed quickly.

Impact Assessment

The impact of a successful exploit is critical. An attacker with code execution on the ingress controller pod can:

• Intercept Traffic: Read, modify, or redirect any and all traffic passing through the ingress, including traffic containing sensitive data like credentials, PII, and API keys.
• Access Cluster Secrets: The ingress controller pod often has access to TLS certificates and other secrets stored within the Kubernetes cluster.
• Lateral Movement: The compromised pod can be used as a beachhead to attack other services within the cluster network. If the pod is running with a privileged service account, the attacker may be able to query the Kubernetes API server, create new pods, and potentially achieve a full cluster takeover.

Cyber Observables for Detection

Detection Methods

1. Kubernetes Audit Logging: Enable and analyze Kubernetes audit logs. Look for suspicious activity originating from the ingress controller's service account, such as creating, updating, or deleting resources outside of its normal behavior.
2. Container Runtime Security: Use a container runtime security tool (e.g., Falco, Trivy) to monitor for anomalous behavior within the ingress controller pods, such as unexpected process execution, file modifications, or outbound network connections.
3. Review Ingress Objects: Regularly audit Ingress objects for suspicious annotations or configurations, especially in multi-tenant clusters where non-admin users can create them.

Remediation Steps

1. Patch Immediately: The primary remediation is to upgrade the Ingress-NGINX controller to a patched version as soon as it is released. Follow the official project's guidance for upgrading.
2. Restrict Permissions: As a general best practice, limit the permissions of users who can create and modify Ingress objects. Use RBAC policies to ensure that only trusted administrators can manage ingress configuration.
3. Network Policies: Implement Kubernetes Network Policies to restrict traffic from the ingress controller pods. They should only be allowed to communicate with the specific backend services they are configured to route to, not the entire cluster network.