CVE-2022-0759 in kubeclient
Summary
by MITRE • 03/25/2022
A flaw was found in all versions of kubeclient up to (but not including) v4.9.3, the Ruby client for Kubernetes REST API, in the way it parsed kubeconfig files. When the kubeconfig file does not configure custom CA to verify certs, kubeclient ends up accepting any certificate (it wrongly returns VERIFY_NONE). Ruby applications that leverage kubeclient to parse kubeconfig files are susceptible to Man-in-the-middle attacks (MITM).
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Analysis
by VulDB Data Team • 03/27/2022
The vulnerability identified as CVE-2022-0759 represents a critical security flaw in the kubeclient Ruby library that affects versions prior to v4.9.3. This issue stems from improper certificate validation handling within the Kubernetes REST API client implementation, creating a significant attack surface for malicious actors. The flaw specifically manifests when kubeconfig files lack explicit custom certificate authority configurations, leading to an insecure default behavior that undermines the fundamental security model of Kubernetes cluster communications.
The technical root cause of this vulnerability lies in the kubeclient library's certificate parsing logic which incorrectly returns VERIFY_NONE when no custom CA is specified in the kubeconfig file. This erroneous behavior effectively disables SSL certificate verification, allowing attackers to intercept and manipulate communications between Ruby applications and Kubernetes APIs. The vulnerability maps directly to CWE-295 which addresses improper certificate validation, and aligns with ATT&CK technique T1566 related to credential access through man-in-the-middle attacks. When applications parse kubeconfig files through this library, they inadvertently accept any certificate presented by an attacker, completely bypassing the security mechanisms designed to protect against unauthorized access to cluster resources.
The operational impact of this vulnerability extends beyond simple certificate verification failure, creating a pathway for sophisticated attack vectors that could compromise entire Kubernetes environments. Ruby applications utilizing kubeclient for cluster management, deployment operations, or monitoring functions become vulnerable to active man-in-the-middle attacks where attackers can intercept sensitive data, modify cluster configurations, or gain unauthorized access to workloads. This risk is particularly severe in production environments where Kubernetes clusters manage critical infrastructure components, as the vulnerability could enable attackers to escalate privileges, exfiltrate confidential data, or disrupt service availability through malicious configuration changes.
Organizations should immediately implement mitigation strategies focusing on both immediate remediation and long-term security posture improvements. The primary recommendation involves upgrading all affected applications to kubeclient version 4.9.3 or later, which contains the patched certificate validation logic. Additionally, security teams should conduct comprehensive audits of all Ruby applications that utilize kubeclient to identify potential exposure points and implement proper certificate validation enforcement. Network-level protections such as certificate pinning, enhanced monitoring for unusual certificate validation patterns, and regular security scanning of containerized environments can provide additional defense layers. The vulnerability underscores the importance of maintaining updated dependencies and implementing robust security controls around API client configurations, particularly in environments where automated deployment and management tools rely on secure communication protocols.