Summary
Users of Kyverno on versions 1.8.3 or 1.8.4 who use verifyImages rules to verify container image signatures, and do not prevent use of unknown registries, are affected.
Impact
A malicious proxy or registry can supply unsigned or attacker-controlled images that pass through verifyImages when the cluster permits arbitrary registry sources. Operators relying on verifyImages as their only image-trust gate could admit untrusted images, defeating the supply-chain control they thought was in place.
Detection
Audit cluster admission policies for an explicit allow-list of trusted registries. The absence of one — or the presence of broad wildcards — is the prerequisite. Inspect Kyverno policy reports for verifyImages decisions on images sourced from non-canonical registries.
Mitigation
Upgrade Kyverno to v1.8.5 or later.
Workaround: configure a Kyverno policy to restrict registries to a set of secure trusted image registries — see the upstream restrict-image-registries sample policy. Pair verifyImages with explicit registry pinning so a malicious proxy cannot interpose.