CVE-2026-39961: Aiven Operator has cross-namespace secret exfiltration via ClickhouseUser connInfoSecretSource

A developer with create permission on ClickhouseUser CRDs in their own namespace can exfiltrate secrets from any other namespace — production database credentials, API keys, service tokens — with a single kubectl apply. The operator reads the victim’s secret using its ClusterRole and writes the password into a new secret in the attacker’s namespace.

The operator acts as a confused deputy: its ServiceAccount has cluster-wide secret read/write (aiven-operator-role ClusterRole), and it trusts user-supplied namespace values in spec.connInfoSecretSource.namespace without validation. No admission webhook enforces this boundary — the ServiceUser webhook returns nil, and no ClickhouseUser webhook exists.