Kyverno API Call Vulnerability Exposes Kubernetes Clusters

The National Vulnerability Database has detailed CVE-2026-41323, a critical vulnerability in Kyverno, the Kubernetes policy engine. Prior to versions 1.18.0-rc1, 1.17.2-rc1, and 1.16.4, Kyverno’s apiCall feature in ClusterPolicy automatically appended the admission controller’s ServiceAccount token to outgoing HTTP requests. The critical flaw lies in the lack of validation for the service URL, which could be directed to arbitrary, including attacker-controlled, servers.

This oversight means that an attacker could exfiltrate the admission controller’s ServiceAccount token. Given that this ServiceAccount typically possesses permissions to patch webhook configurations, a stolen token provides a direct pathway to full cluster compromise. The National Vulnerability Database assigns this a CVSS score of 8.1 (HIGH), underscoring the severe implications for confidentiality and integrity. The vulnerability is tracked as CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) and CWE-918 (Server-Side Request Forgery).

Defenders need to understand the attacker’s calculus here: exfiltrating a privileged ServiceAccount token is a high-value target for lateral movement and privilege escalation. This isn’t theoretical; it’s a clear path to taking over a cluster. Patching is non-negotiable. Organizations running affected Kyverno versions must upgrade immediately to mitigate this severe risk.