Kubernetes Moves Image Verification to Runtime with NRI Plugin

A recent CNCF post proposes shifting container image signature and attestation checks from Kubernetes admission webhooks to the container runtime itself using a Node Resource Interface (NRI) plugin. The plugin hooks the CreateContainer event in CRI-O or containerd, pulls image metadata, fetches SLSA provenance, VEX and VSA attestations from the OCI registry, and blocks the container from starting if verification fails.

The move addresses known bypasses of admission‑webhook‑based security, including static pods managed directly by the kubelet, direct kubelet access, mis‑configured namespace selectors, and webhook outages that force operators to choose between cluster lock‑up or silent bypass. Runtime‑level verification, however, introduces new operational dependencies: the plugin must be healthy on every node, maintain credentials and network connectivity to the registry, and handle registry outages without causing cluster‑wide start failures.