Impact

Cilium allows outside actors (world entity) to directly access pods with their internal pod IP, even if they are not exposed explicitly (e.g. via LoadBalancer). A pod that does not authenticate clients and that does not exclude world traffic via network policy may leak sensitive data to an attacker inside the cloud VPC.

Patches

The issue has been patched in v2.16.3.

Workarounds

This network policy excludes all world traffic. It mitigates the problem, but will also block all desired external traffic. If vulnerable pods are known, a policy can be crafted to only firewall those instead (see also https://docs.cilium.io/en/stable/security/policy/language/#access-to-from-outside-cluster).

apiVersion: "cilium.io/v2"
kind: CiliumClusterwideNetworkPolicy
metadata:
  name: "from-world-to-role-public"
spec:
  endpointSelector:
    matchLabels: {}
    #  role: public
  ingressDeny:
    - fromEntities:
      - world

References

The tracking bug for a Cilium-side fix is cilium/cilium#25626.