CVE-2024-5042: Submariner Unauthorized Access due to Unnecessary Role-Based Access Control Permissions - Vulnerability, Exploits, and Mitigation

A critical flaw has been identified in the Submariner project which potentially grants a privileged attacker the ability to compromise an entire cluster by exploiting unnecessary role-based access control (RBAC) permissions. This vulnerability, designated as CVE-2024-5042, allows the attacker to run a malicious container on a node, steal service account tokens, and subsequently compromise other nodes within the cluster.

This post will analyze the vulnerability in detail, delve into the attack vector, and explore potential exploits. In addition, it will provide guidance on how to mitigate the issue and protect your Kubernetes cluster from this CVE.

Vulnerability Details

The primary issue lies with the Submariner project's implementation of RBAC. By granting unnecessary and overly broad permissions to certain service accounts, it opens the door for a privileged attacker to exploit these permissions and execute malicious commands across the entire cluster.

Here is a code snippet that demonstrates the problematic RBAC permissions

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: submariner-operator:cluster-role
rules:
- apiGroups:
  - ""
...
  resources:
  - secrets
  verbs:
  - create
  - delete
  - get
  - list
  - patch
  - update
  - watch
...

As seen in the code snippet above, the Submariner operator's ClusterRole contains permissions to secrets resources. These permissions (create, delete, get, list, patch, update, and watch) are overly broad, allowing the attacker to manipulate critical cluster resources and secrets.

Exploit Details

By using a malicious container, the attacker can abuse these broad permissions to steal service account tokens (e.g., for the Submariner operator), which can then be used to carry out operations on other nodes and potentially compromise the entire cluster. This can lead to severe security consequences, including unauthorized access, data breaches, and cluster downtime.

Spawn a malicious container on the same node as the Submariner operator.

$ kubectl run my-malicious-container --image=malicious_image

Run a script inside the container to extract the service account token for the Submariner operator.

$ kubectl exec -it my-malicious-container -- /bin/bash
# ./extract_service_account_token.sh

3. Use the stolen service account token to access cluster resources and potentially compromise other nodes.

Here are some original references related to CVE-2024-5042

- Submariner GitHub Repo
- CVE-2024-5042 Official Documentation

Mitigation

In order to protect your cluster from this severe vulnerability, consider implementing the following measures:

1. Limit RBAC permissions: Review your cluster's service accounts and roles, ensuring only necessary and minimal permissions are granted. Specifically, verify the submariner-operator:cluster-role permissions and reduce their scope.

2. Patch and update: Regularly check for updates and security patches for the Submariner project and apply them as soon as they become available.

3. Monitor and log: Keep a close eye on your cluster's activity logs and monitor for any suspicious behavior. Investigate and remediate any detected anomalies promptly.

Conclusion

CVE-2024-5042 is a critical vulnerability in the Submariner project that can lead to the compromise of an entire Kubernetes cluster if left unchecked. By understanding the exploit details and implementing the provided mitigation techniques, you can significantly reduce your cluster's risk exposure and maintain a secure environment for your applications and data.

Timeline

Published on: 05/17/2024 14:15:21 UTC
Last modified on: 08/02/2024 16:14:59 UTC