A critical flaw in the Kyverno policy engine for Kubernetes lets a tenant confined to one namespace break out and take over the whole cluster. Tracked as CVE-2026-124440, it carries a CVSS score of 9.4 and was published on 8 November 2026.

The bug sits in the namespace clamp on a policy's apiCall feature, which lets policies fetch data from the Kubernetes API. Kyverno checks the requested urlPath after cleaning it, but then executes the raw path, so a namespace-scoped user who can create a policy can smuggle path-traversal segments past the check. The call then runs with the privileges of Kyverno's own admission-controller service account.

That is enough to read resources in other namespaces and to create cluster-wide mutating webhooks, which an attacker can use to rewrite admitted workloads and escalate to cluster admin. Only Kyverno 1.19.1 is affected; earlier and later versions are not hit by this particular flaw.

Administrators should upgrade to Kyverno 1.19.2, which contains the fix. The flaw is a fresh entry in the same apiCall area that produced a batch of seven Kyverno flaws disclosed on 5 November, and it underlines why multi-tenant clusters should treat namespace boundaries as a security control, not a convenience. There is no reported public exploit and the flaw is not on CISA's exploited-vulnerabilities list, but the upgrade is straightforward and should not wait.