Kyverno before 1.19.2 Denial of Service via Nested Variable Substitution Loop

Summary

Kyverno before 1.19.2 contains a denial of service vulnerability in substituteVariablesIfAny that allows low-privileged users to hang the admission webhook via self-referential variable templates. Attackers can create resources whose annotations re-introduce the embedded policy variable, causing unbounded substitution loops that exhaust CPU and memory and block cluster-wide admission.

Remediation

1. Inventory every kyverno kyverno deployment, including staging.
2. Upgrade kyverno kyverno to 1.19.2.
3. Confirm the running version after the upgrade.

References

• Advisoryhttps://github.com/kyverno/kyverno/security/advisories/GHSA-338x-hgrv-626h
• Advisoryhttps://www.vulncheck.com/advisories/kyverno-before-1.19.2-denial-of-service-via-nested-variable-substitution-loop