Fullchain's Invalid NetworkPolicy enables a malicious actor to pivot into another namespace

Impact

Due to a mis-written NetworkPolicy, a malicious actor can pivot from a subverted application to any Pod out of the origin namespace. This breaks the security-by-default property expected as part of the deployment program, leading to a potential lateral movement.

Patch

Removing the inter-ns NetworkPolicy patches the vulnerability. If updates are not possible in production environments, we recommend to manually delete it and update as soon as possible.

Workaround

Given your context, delete the failing network policy that should be prefixed by inter-ns- in the target namespace. You can use the following to delete all matching network policy. If unsure of the outcome, please do it manually.

for ns in $(kubectl get ns -o jsonpath='{.items[*].metadata.name}' | tr ' ' '\n' | grep '^ns-'); do
  kubectl -n "$ns" get networkpolicy -o name \
  | grep '^networkpolicy.networking.k8s.io/inter-ns-' \
  | xargs -r kubectl -n "$ns" delete
done