Kyverno versions prior to 1.19.2 contain a missing authorization flaw (CWE-862) in the mutate-existing background processor. The flaw enables a tenant confined to a single namespace to create a NamespacedMutatingPolicy that targets Namespace objects or resources in any namespace through CEL expressions. The background-controller ServiceAccount can then strip Pod Security labels cluster‑wide, effectively allowing cross‑namespace writes and compromising the integrity of the entire cluster.

The vulnerability affects Kyverno 1.17.0 through 1.19.1 for the kyverno:kyverno product. All deployments of these versions are potentially exposed if they run the mutate-existing background processor.

The CVSS score of 8.4 categorizes this as a high‑severity issue. Although no EPSS score is reported and the vulnerability is not listed in the CISA KEV catalog, the nature of the flaw—cross‑namespace write once an attacker gains access to a namespaced ServiceAccount—suggests a high likelihood of exploitation in environments where tenant isolation is critical. The attack vector would involve creating a malicious NamespacedMutatingPolicy; prerequisites are limited to the ability to submit such a policy in the tenant’s namespace, which is typically allowed by default in Kyverno installations.