Empirical Analysis and Mitigation Strategies for Kube-API server Vulnerabilities: Countering Security Posture Risks

Abstract

: For every Kubernetes cluster, Kube-API server acts as its heart, considered to be a single-entry point across cluster where all communication related to workload state & policies are enforced. When organization needs increases to address multi-tenant and production grade environments, it is must to focus on security risk involved in critical components like Kube-API. Considering API server importance, there are numerous opportunities to penetrate this component considering its architectural behaviour leading to security risks. This paper focuses on three such security posture risks, first one is related to API server deployments where mixed-versions during the component rolling upgrades causes the network traffic to route towards older cluster instances without proper validation checks/admission controls bypassing existing policies. The second concern is related to configuration set for API priority and fairness (APF), where shared priority queues across cluster can be compromised by a single noisy client causing other clients to hit denial-service issues. The third security risk is leakage of critical API server information via monitoring tool metrics; this information may be related to sensitive cluster workload details in a namespace/label to users with read-only access. For the mentioned vulnerabilities, this article performs complete analysis finding their underlying root cause, testing the issue and reproducing in internal environments and providing remediation strategies. The strategies are focused at workload configuration setup, analysing existing YAML structures, and suggesting code level fixes. The CVE analysis and findings highlight; API server requires focus and strategies to be implemented during upgrade flows, existing observability metric architecture and traffic related isolation.