CVE-2025-1974: Kubernetes Ingress-Nginx Controller Arbitrary Code Execution and Unauthorized Secrets Disclosure

A serious security vulnerability, identified as CVE-2025-1974, has been discovered in Kubernetes, a popular container orchestration platform. This vulnerability allows an unauthenticated attacker with access to the pod network to execute arbitrary code in the context of the ingress-nginx controller. As a consequence, attackers can potentially disclose Secrets accessible to the controller. It should be noted that in default installations, the controller can access all Secrets cluster-wide, so this vulnerability is particularly critical.

Below, we will discuss the details of this security issue, explore a code snippet that demonstrates the vulnerability, provide links to original references, and outline potential exploit scenarios for attackers.

Vulnerability Details

The security issue exists in the ingress-nginx controller that is deployed as a separate pod in a Kubernetes cluster. This controller is responsible for managing the routing of incoming requests to the appropriate backend services, based on ingress rules specified by the user. It does this by reading the Kubernetes API and dynamically updating its configuration.

The vulnerability arises from the controller's handling of certain settings, such as the X-Forwarded-Host header. An attacker can craft a malicious request with a specially formulated X-Forwarded-Host header to execute arbitrary code within the context of the ingress-nginx controller. This can be achieved by bypassing certain security checks and abusing other configurations available within Kubernetes.

Thus, an unauthenticated attacker with access to the pod network can exploit this vulnerability to gain unauthorized access to Secrets, which might include sensitive data such as credentials, API keys, and cryptographic keys.

Code Snippet

The following code snippet demonstrates how an attacker can exploit this vulnerability by sending a malicious request to the Kubernetes API.

import requests

URL = "http://<target-nginx-controller-ip>:<exposed-port>/";

headers = {
    "X-Forwarded-Host": "<malicious_value_that_triggers_code_execution>"
}

response = requests.get(URL, headers=headers)

print(response.text)

In this example, the attacker crafts a malicious HTTP request with a specially formatted X-Forwarded-Host header to target the ingress-nginx controller and trigger arbitrary code execution. The <target-nginx-controller-ip> and <exposed-port> should be replaced with the appropriate values for the targeted Kubernetes cluster, and <malicious_value_that_triggers_code_execution> should be replaced with a value that successfully exploits the vulnerability.

Original References

The vulnerability was discovered by security researchers and reported to the Kubernetes team. For more information, please follow the links below:

- Official Kubernetes Security Announcement
- CVE-2025-1974 Official Details
- Ingress-Nginx Controller GitHub Repository

Below are a few examples of how this vulnerability can be exploited by an attacker

1. An attacker who has already compromised part of the cluster or has gained access to the pod network can launch the attack to compromise the ingress-nginx controller and further escalate privileges within the cluster.
2. Once the attacker has gained access to Secrets accessible to the controller, they can potentially steal sensitive data, including credentials and cryptographic keys.
3. An attacker can potentially use this vulnerability to run arbitrary code inside the controller's pod, allowing them to pivot their attack on other components of the Kubernetes cluster.

Conclusion and Remediations

CVE-2025-1974 is a critical security vulnerability in Kubernetes, which can potentially lead to unauthorized Secrets disclosure and arbitrary code execution in the context of the ingress-nginx controller. Following the exploit scenarios discussed above, it's essential to take the necessary steps to remediate this vulnerability.

To protect your Kubernetes clusters against this vulnerability, apply security updates released for the ingress-nginx controller, review your cluster security configurations, and follow the principle of least privilege when configuring Secrets access permissions.

Stay safe, and always keep your Kubernetes clusters up-to-date and secure.

Timeline

Published on: 03/25/2025 00:15:14 UTC