Executive brief
Kyverno is a Kubernetes policy engine that enforces security and compliance rules. A flaw in URL path validation allows authenticated namespace users to bypass restrictions and create configuration objects cluster-wide, which can be leveraged to escalate privileges to cluster administrator. An attacker can register malicious webhook configurations to intercept and modify Kubernetes objects across all namespaces.
Technical details
Kyverno fails to properly validate percent-encoded path segments in Policy apiCall urlPath, allowing namespace-confined users to traverse beyond their namespace boundary. By injecting %2e%2e segments, an attacker can reach cluster-scoped API endpoints and create MutatingWebhookConfiguration or PolicyException objects as the admission-controller ServiceAccount. This enables privilege escalation to cluster admin through webhook-based object rewriting or policy exception bypass.
Affected products
- Kyverno Kyverno before 1.19.1
Timeline
- 2026-09-10: disclosed
- 2026-09-10: patched: version 1.19.1