Critical Vulnerability in Rancher Kubernetes Engine Risks Exposure of Sensitive Credentials

June 19, 2024

A critical flaw, identified as CVE-2023-32191, has been detected in the Rancher Kubernetes Engine (RKE). RKE, a popular Kubernetes distribution, simplifies the installation and operation of Kubernetes. It is known for running Kubernetes completely within Docker containers on both physical and virtual servers. However, a significant security issue lies in how it stores cluster state information. This vulnerability has been given the maximum CVSS score of 10, indicating a severe threat to the security and integrity of Kubernetes clusters managed by RKE.

The vulnerability stems from the fact that RKE stores sensitive credentials within a ConfigMap named full-cluster-state in the kube-system namespace of the cluster. This ConfigMap contains a range of sensitive data. The presence of these credentials in a ConfigMap implies that anyone with read access to this ConfigMap effectively obtains administrative-level control over the entire Kubernetes cluster. Such a level of access can result in serious breaches in confidentiality, integrity, and availability, potentially exposing an organization’s entire cloud infrastructure to malicious actors.

The full-cluster-state ConfigMap holds the entire state of the Kubernetes cluster, encompassing critical configuration details and credentials necessary for cluster operations. While access to this ConfigMap usually requires permissions within the RKE cluster, it is not exclusively limited to administrators. Non-administrative users with the capability to read this ConfigMap can exploit it to gain unauthorized access and control over the cluster.

To address the CVE-2023-32191 vulnerability, RKE users are advised to upgrade to the patched versions. These updates involve changes that shift the cluster state from a ConfigMap to a more secure secret in the kube-system namespace. Access to this secret is limited to users with appropriate permissions, specifically admin and cluster-owner roles in Rancher. For those who cannot upgrade immediately, there are no effective workarounds. Therefore, it is of utmost importance to prioritize upgrading RKE to safeguard your Kubernetes environments from potential exploitation.

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