Critical ingress-nginx flaws enable Kubernetes cluster takeover

Kubernetes maintainers disclosed five critical vulnerabilities in ingress-nginx, including CVE-2025-1974 with a CVSS 9.8 rating, warning that attackers on the Pod network could abuse configuration injection in the Validating Admission Controller to take over clusters without credentials. The flaws also affect how ingress-nginx builds NGINX configuration from crafted Ingress objects, potentially exposing Secrets available to the controller and leading to full cluster compromise. Patched releases ingress-nginx v1.12.1 and v1.11.5 were issued, and operators were urged to upgrade immediately or temporarily disable the Validating Admission Controller until patching is complete.

The disclosure adds to broader concerns about Kubernetes networking and multi-tenant isolation, highlighted by CVE-2021-25740, an unpatchable issue that lets users with permission to modify Endpoint or EndpointSlice objects redirect service traffic to unauthorized IP addresses. In shared ingress-controller or load-balancer deployments, that behavior can allow one tenant to steer traffic into another tenant’s workloads and bypass intended network boundaries. Security researchers and vendors said the combined risk is highest in clusters that rely on shared ingress infrastructure with broad Secret access, and recommended tightening EndpointSlice permissions, avoiding shared ingress designs in sensitive environments, and evaluating the Gateway API as a safer architecture.