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CVE-2025-1974: ingress-nginx admission controller RCE escalation

· 3 min read
Ivan Sim
important

CVE-2025-1974 (vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) has a score of 9.8 (Critical).

The vulnerability affects specific versions of the RKE2 ingress-nginx controller (v.1.11.4 and earlier, and v1.12.0). All Harvester versions that use this controller (including v1.4.2 and earlier) are therefore affected.

This CVE is fixed in Harvester 1.5.0, 1.4.3 and newer.

A security issue was discovered in Kubernetes where under certain conditions, an unauthenticated attacker with access to the pod network can achieve arbitrary code execution in the context of the ingress-nginx controller. This can lead to disclosure of secrets accessible to the controller. (Note that in the default installation, the controller can access all secrets cluster-wide.)

You can confirm the version of the RKE2 ingress-nginx pods by running this command on your Harvester cluster:

kubectl -n kube-system get po -l"app.kubernetes.io/name=rke2-ingress-nginx" -ojsonpath='{.items[].spec.containers[].image}'

If the command returns one of the affected versions, disable the rke2-ingress-nginx-admission validating webhook configuration by performing the following steps:

  1. On one of your control plane nodes, use kubectl to confirm the existence of the HelmChartConfig resource named rke2-ingress-nginx:

    $ kubectl -n kube-system get helmchartconfig rke2-ingress-nginx
    NAME                 AGE
    rke2-ingress-nginx   14d1h

  2. Use kubectl -n kube-system edit helmchartconfig rke2-ingress-nginx to add the following configurations to the resource:

    • .spec.valuesContent.controller.admissionWebhooks.enabled: false
    • .spec.valuesContent.controller.extraArgs.enable-annotation-validation: true

  3. The following is an example of what the updated .spec.valuesContent configuration along with the default Harvester ingress-nginx configuration should look like:

    apiVersion: helm.cattle.io/v1
    kind: HelmChartConfig
    metadata:
      name: rke2-ingress-nginx
      namespace: kube-system
    spec:
      valuesContent: |-
        controller:
          admissionWebhooks:
            port: 8444
            enabled: false
          extraArgs:
            enable-annotation-validation: true
            default-ssl-certificate: cattle-system/tls-rancher-internal
          config:
            proxy-body-size: "0"
            proxy-request-buffering: "off"
          publishService:
            pathOverride: kube-system/ingress-expose

    Exit the kubectl edit command execution to save the configuration.

    Harvester automatically applies the change once the content is saved.

    important

    The configuration disables the RKE2 ingress-nginx admission webhooks while preserving Harvester's default ingress-nginx configuration.

    If the HelmChartConfig resource contains other custom ingress-nginx configuration, you must retain them when editing the resource.

  4. Verify that RKE2 deleted the rke2-ingress-nginx-admission validating webhook configuration.

    $ kubectl get validatingwebhookconfiguration rke2-ingress-nginx-admission
    Error from server (NotFound): validatingwebhookconfigurations.admissionregistration.k8s.io "rke2-ingress-nginx-admission" not found

  5. Verify that the ingress-nginx pods are restarted successfully.

    $ kubectl -n kube-system get po -lapp.kubernetes.io/instance=rke2-ingress-nginx
    NAME                                  READY   STATUS    RESTARTS   AGE
    rke2-ingress-nginx-controller-g8l49   1/1     Running   0          5s

Once your Harvester cluster receives the RKE2 ingress-nginx patch, you can re-install the rke2-ingress-nginx-admission validating webhook configuration by removing the HelmChartConfig patch.

important

These steps only cover the RKE2 ingress-nginx controller that is managed by Harvester. You must also update other running ingress-nginx controllers. See the References section for more information.

References​