External Secrets Operator reads information from a third-party service and automatically injects the values as Kubernetes Secrets. Starting in version 0.20.2 and prior to version 1.2.0, the getSecretKey template function, while introduced for senhasegura Devops Secrets Management (DSM) provider, has the ability to fetch secrets cross-namespaces with the roleBinding of the external-secrets controller, bypassing our security mechanisms. This function was completely removed in version 1.2.0, as everything done with that templating function can be done in a different way while respecting External Secrets Operator's safeguards As a workaround, use a policy engine such as Kubernetes, Kyverno, Kubewarden, or OPA to prevent the usage of getSecretKey in any ExternalSecret resource.
Details The external-secrets has a deployment called default-external-secrets-cert-controller, which is bound with a same-name ClusterRole. This ClusterRole has "get/list" verbs of secrets resources(https://github.com/external-secrets/external-secrets/blob/main/deploy/charts/external-secrets/templates/cert-controller-rbac.yaml#L49). It also has path/update verb of validatingwebhookconfigurations resources(https://github.com/external-secrets/external-secrets/blob/main/deploy/charts/external-secrets/templates/cert-controller-rbac.yaml#L27). As a result, if a malicious user can access the worker node which has this deployment. he/she can: 1. For the "get/list secrets" permission, he/she can abuse the SA token of this deployment to retrieve or get ALL secrets in the whole cluster, including the cluster-admin secret if created. After that, he/she can abuse the cluster-admin secret to do whatever he/she likes to the whole cluster, resulting in a cluster-level privilege escalation.
2. For the patch/update verb of validatingwebhookconfigurations, the malicious user can abuse these permissions to get sensitive data or lanuch DoS attacks:
For the privilege escalation attack, by updating/patching a Webhook to make it listen to Secret update operations, the attacker can capture and log all data from requests attempting to update Secrets. More specifically, when a Secret is updated, this Webhook sends the request data to the logging-service, which can then log the content of the Secret. This way, an attacker could indirectly gain access to the full contents of the Secret.
For the DoS attack, by updating/patching a Webhook, and making it deny all Pod create and update requests, the attacker can prevent any new Pods from being created or existing Pods from being updated, resulting in a Denial of Service (DoS) attack.
PoC Please see the "Details" section
Impact Privilege escalation