CVE-2017-1000056 in Kubernetes
Summary
by MITRE
Kubernetes version 1.5.0-1.5.4 is vulnerable to a privilege escalation in the PodSecurityPolicy admission plugin resulting in the ability to make use of any existing PodSecurityPolicy object.
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Analysis
by VulDB Data Team • 12/12/2022
The vulnerability identified as CVE-2017-1000056 affects Kubernetes versions 1.5.0 through 1.5.4 and represents a critical privilege escalation flaw within the PodSecurityPolicy admission plugin. This vulnerability stems from insufficient validation mechanisms that allow unauthorized users to exploit existing PodSecurityPolicy objects to gain elevated privileges within the cluster. The issue specifically targets the admission control mechanism that enforces security policies for pod creation and execution, creating a pathway for malicious actors to bypass intended security controls.
The technical flaw manifests in the improper handling of PodSecurityPolicy objects during the admission process, where the system fails to adequately verify whether the requesting user has the appropriate permissions to utilize specific security policies. This weakness creates a scenario where an attacker with limited access can manipulate the system to apply restrictive policies that they should not be able to use, effectively circumventing the intended security boundaries. The vulnerability is categorized under CWE-284 Access Control, specifically addressing improper access control mechanisms within the Kubernetes admission controller framework.
The operational impact of this vulnerability is severe as it enables attackers to escalate their privileges from limited user access to potentially full cluster control. An attacker could leverage this flaw to create pods that bypass security restrictions, access sensitive data, or gain unauthorized access to cluster resources. The exploitation of this vulnerability directly contradicts the fundamental security principles of Kubernetes' admission control system, which is designed to enforce security policies and prevent unauthorized actions within the cluster environment.
Organizations using affected Kubernetes versions should immediately implement mitigations including upgrading to patched versions of Kubernetes, implementing additional access controls, and monitoring for unauthorized policy modifications. The vulnerability aligns with ATT&CK technique T1078 Valid Accounts, as it allows attackers to leverage existing legitimate accounts to escalate privileges. Security teams should also review and validate all existing PodSecurityPolicy configurations to ensure that only authorized users can utilize specific security policies, implementing the principle of least privilege to minimize potential damage from such vulnerabilities.