CVE-2016-1905 in Kubernetes
Summary
by MITRE
The API server in Kubernetes does not properly check admission control, which allows remote authenticated users to access additional resources via a crafted patched object.
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Analysis
by VulDB Data Team • 07/07/2022
The vulnerability identified as CVE-2016-1905 resides within the Kubernetes API server component, specifically targeting the admission control mechanisms that are fundamental to maintaining security boundaries within the container orchestration platform. This flaw represents a critical weakness in the platform's authorization model, where the API server fails to adequately validate and enforce access controls when processing patch operations on Kubernetes objects. The vulnerability affects the admission control system that is designed to intercept and validate requests before they are processed, creating a potential bypass that allows authenticated attackers to escalate their privileges and access resources they should not be authorized to view or modify.
The technical implementation of this vulnerability stems from insufficient validation of patch operations within the admission control pipeline. When users submit patch requests to the Kubernetes API server, the system should validate that the requesting user has appropriate permissions for the modifications being requested. However, in this case, the admission controller does not properly verify the permissions associated with patch operations, allowing maliciously crafted patch objects to bypass these security checks. This flaw particularly impacts the authorization mechanisms that govern access to Kubernetes resources such as pods, services, namespaces, and other cluster objects. The vulnerability is classified under CWE-284, which deals with improper access control, and aligns with ATT&CK technique T1078 for valid accounts and T1566 for credential access through exploitation of software vulnerabilities.
The operational impact of CVE-2016-1905 is significant for organizations running Kubernetes clusters, as it provides authenticated attackers with the ability to access additional resources beyond their intended permissions. This could enable attackers to view sensitive information, modify critical cluster components, or potentially gain access to other resources within the cluster that they would normally be restricted from accessing. The vulnerability is particularly dangerous because it requires only authenticated access to the Kubernetes API server, which is often accessible to various users within an organization. Attackers could exploit this vulnerability to escalate privileges, access confidential data stored in the cluster, or manipulate cluster configurations to compromise the overall security posture. The impact extends beyond simple information disclosure, as the ability to modify resources could lead to service disruption, data manipulation, or even complete cluster compromise.
Organizations should implement immediate mitigations including applying the latest security patches released by the Kubernetes project, which typically address the admission control validation issues. Network segmentation and access control measures should be strengthened to limit access to the Kubernetes API server to only trusted users and systems. Regular monitoring of API server logs for suspicious patch operations and unauthorized access attempts should be implemented as part of the security operations center procedures. Additionally, organizations should conduct comprehensive access control reviews to ensure that users have only the minimum necessary permissions and that the principle of least privilege is properly enforced. The vulnerability highlights the importance of proper admission control implementation and serves as a reminder of the critical security considerations that must be addressed in container orchestration platforms to prevent unauthorized access and privilege escalation scenarios.