NGINX Ingress Controller: unsanitized CRD and annotation fields inject arbitrary NGINX directives

Impact

An authenticated Kubernetes user who can create or modify Ingress resources or the controller's CRDs can write arbitrary directives into the generated NGINX configuration. Per F5, that reaches file creation and deletion and service disruption inside the controller pod - the controller runs with cluster-wide read access to Ingress objects and TLS secrets, so a tenant with namespaced Ingress write permission escalates into the shared ingress tier. On a GPU cluster the ingress controller is typically the single front door for every tenant's inference endpoint, so one tenant can break or redirect everyone's traffic. F5 states there is no data plane exposure; this is a control plane issue.

Who can reach it

Authenticated Kubernetes API user with RBAC permission to create or edit Ingress annotations or NGINX Ingress CRDs in any namespace the controller watches. No access to the node or the data plane is needed.

What to do

Upgrade NGINX Ingress Controller to a fixed release per F5 K000161800 and roll the controller deployment - a rolling restart of the ingress pods, no node drain. Until then, restrict who can create or edit Ingress annotations and the controller's CRDs, and enable the controller's annotation/snippet restrictions so untrusted namespaces cannot supply raw configuration. Versions past End of Technical Support were not evaluated.

References

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