Kyverno versions prior to 1.19.2 contain an authorization bypass in the apiCall namespace clamp. By appending malformed percent‑escapes to the urlPath of a policy’s apiCall, a tenant can issue API requests that normally would be confined to their namespace. According to the advisory, an attacker who can create namespaced Policies is able to run those calls as the admission‑controller ServiceAccount, allowing them to read resources in other namespaces and deploy mutating webhooks. This effectively provides access to cluster‑level resources and can lead to a full cluster‑admin compromise.

Vendor Kyverno, product kyverno, affected versions 1.19.1 and earlier. Versions 1.19.2 and later contain the fix.

The CVSS score is 9.4, indicating critical severity. EPSS data is not available, and the vulnerability is not listed in CISA KEV. The likely attack vector is a legitimate API request sent from within a vulnerable namespace, exploiting the malformed urlPath. Successful exploitation requires the ability to create a namespaced policy, which may be granted to users in somewhat permissive RBAC configurations. Once the apiCall is executed, the attacker can obtain namespace‑wide reading privileges and instantiate cluster‑level webhook services, leading to systemic privilege escalation.