A critical vulnerability in Kyverno, a cloud-native policy engine, allows users with Policy or ClusterPolicy creation permissions to crash cluster controllers through an unchecked type assertion in the forEach mutation handler. The vulnerability affects versions prior to 1.17.2 and 1.16.4, causing persistent CrashLoopBackOff states and blocking resource operations. The issue is confined to the legacy engine, with CEL-based policies remaining unaffected. Fixed versions are available.