CVE-2023-3955: Critical Privilege Escalation Vulnerability in Kubernetes Affecting Windows Nodes

A high-severity security vulnerability (CVE-2023-3955) has been discovered in Kubernetes that can allow attackers to escalate their privileges on Windows nodes. This issue currently affects those Kubernetes clusters that include Windows nodes, and if exploited, it could lead to various security risks such as unauthorized access to sensitive data and resources. This post aims to provide a detailed overview of this vulnerability, including a code snippet, links to original references, and details about the exploit.

Vulnerability Details

The CVE-2023-3955 vulnerability results from a flaw in the way Kubernetes handles user permissions on Windows nodes, specifically allowing a user with the ability to create pods on these nodes to potentially escalate their privileges to admin level. An attacker can then execute malicious commands on the host, leading to a complete compromise of the Windows node.

The following code snippet demonstrates how an attacker could exploit this vulnerability

apiVersion: v1
kind: Pod
metadata:
  name: windows-priv-escalation-pod
spec:
  containers:
  - name: windows
    image: mcr.microsoft.com/windows/servercore:ltsc2019
    command: ["cmd.exe", "/c", "echo Escalating Privileges... && net user attacker P@sswrd /add && net localgroup Administrators attacker /add"]
  nodeSelector:
    kubernetes.io/os: windows

This example shows a basic YAML file that creates a new pod with a Windows container running a command, which adds a new user "attacker" with administrative privileges on the Windows node.

To exploit this vulnerability, an attacker must

1. Have access to a Kubernetes cluster with Windows nodes and the ability to create pods on those nodes.
2. Craft a malicious YAML file (like the one shown above) that exploits the permission mishandling on the Windows nodes.
3. Apply the YAML file on the Kubernetes cluster, which creates a new pod that escalates its privileges on the Windows node.
4. Gain unauthorized access to the Windows node and perform malicious activities, such as data theft or damage.

Mitigation

The Kubernetes team has released a patch to address this critical vulnerability, and it is strongly recommended that affected users upgrade their Kubernetes installations immediately to protect their clusters from potential attacks.

Conclusion

CVE-2023-3955 is a critical privilege escalation vulnerability in Kubernetes that affects Windows nodes. By exploiting this issue, attackers can potentially gain unauthorized access to sensitive data and resources within the cluster. It's crucial to ensure that your Kubernetes cluster is running on a patched version to avoid falling victim to such attacks. Keep your systems up-to-date and follow best security practices to maintain a secure and reliable infrastructure.

Please feel free to share any feedback or ask questions in the comments section, and stay tuned for further updates on security issues affecting Kubernetes and other popular software platforms.

Timeline

Published on: 10/31/2023 21:15:08 UTC
Last modified on: 11/08/2023 18:29:32 UTC