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1. IL-0053 Unauthenticated ingress-nginx admission webhook let anyone on the pod network run code and read every Secret in the cluster (IngressNightmare, CVE-2025-1974)

   Wiz2025

   Symptoms

   This is a vulnerability report, not an outage, so nothing failed visibly. A cluster is exposed if it runs Ingress NGINX Controller older than 1.12.1 or 1.11.5 with its validating admission webhook enabled. Wiz suggests `kubectl get pods --all-namespaces --selector app.kubernetes.io/name=ingress-nginx` to find it. The webhook accepts AdmissionReview requests over HTTP without authentication from any pod, and Wiz found more than 6,500 clusters exposing it to the public internet.

   Unauthorised access or a foreign workload

   Trigger

   Wiz Research reviewed the code of the Ingress NGINX admission controller and reported the first findings to Kubernetes on 31 December 2024.

   Root cause

   Software defect

   Component

   Ingress controllerAdmission webhook

   Contributing factor

   Unreviewed defaultsExcessive blast radius

   Detection

   Found by Wiz Research in a code review of the admission controller, not by an operator.

   Remediation

   • Kubernetes patched the injection flaws CVE-2025-1097, CVE-2025-1098 and CVE-2025-24514
   • Kubernetes removed NGINX configuration testing from the ingress-nginx admission controller, resolving CVE-2025-1974
   • released Ingress NGINX Controller 1.12.1 and 1.11.5

   Lessons

   Admission webhooks often run as web servers inside the cluster without authentication and with relatively high privileges, so any pod can reach them, and the flaws pair well with SSRF in an application. Wiz concludes that `nginx -t` should be considered harmful when it processes unsanitized user input. Wiz recommends upgrading, keeping the webhook off the internet and allowing only the API server to reach it with network policies. If upgrading must wait, disable the webhook (Helm: controller.admissionWebhooks.enabled=false; manual installs: delete the ValidatingWebhookConfiguration ingress-nginx-admission and remove --validating-webhook from the controller) and enable it again after the upgrade.

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2. IL-0032 Mutating admission controller generated broken JSON patches, silently blocking deploys for a week until a production service ran down to two pods

   Airbnb2020

   Symptoms

   A production service at Airbnb showed a high error rate and could not be deployed. The deploy failed with a cryptic Kubernetes error about being unable to access invalid index 5.

   High error rateThroughput degradationDeploys failing

   Trigger

   A change to the mutating admission controller, which had been rolled out within the previous month, had gone in seven days before the incident surfaced; when it had to delete two items from an array in a spec, it generated an invalid JSON patch that removed index 2 and then index 3.

   Root cause

   Software defect

   Component

   Admission webhookHorizontal pod autoscaler

   Contributing factor

   Change with a delayed effectMonitoring blind spotIgnored early signal

   Detection

   The affected service reported a high error rate and its deploy failed; the slow degradation of other services over the previous seven days had gone unnoticed.

   Remediation

   • deleted the mutating admission controller from the affected cluster

   Action items

   • Create alerts from the existing metrics that would have shown the problem earlier

   Lessons

   Keep in mind that a mutating admission controller exists in the cluster; a recently added one is easy to forget during an incident. Search for the exact error message early instead of working on the visible symptoms. Page a teammate when progress stalls.

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