Kyverno versions 1.17.0 through 1.19.1 allow a tenant to overwrite Kubernetes resources that belong to other namespaces by crafting a NamespacedMutatingPolicy mutate‑existing targetMatchConstraints.expression. The crafted policy lets the attacker supply a CEL map literal with a target specifying an arbitrary namespace, causing the privileged background controller to perform cluster‑wide writes to Secrets, Deployments, or policy objects. This successfully grants the attacker control over sensitive cluster resources, compromising confidentiality, integrity, and availability.

Any Kubernetes cluster running Kyverno 1.17.0 up to and including 1.19.1 is affected. The vulnerability applies regardless of the cluster version or configuration, as long as the vulnerable Kyverno binary is deployed and the tenant namespaces are able to create or edit NamespacedMutatingPolicy objects.

The CVSS score of 9.4 indicates a critical severity. EPSS data are missing, so current exploitation likelihood is unknown, and the vulnerability is not listed in CISA’s KEV. Based on the description, the likely attack vector is a user with the ability to create or modify NamespacedMutatingPolicy resources in their own namespace. With that privilege the attacker can craft an expression that bakes a target pointing to another namespace, and the Kyverno controller will then perform the overwrite as a privileged background process. The attack requires no network access beyond internal control plane connectivity, making it highly feasible in a compromised tenant scenario.