CVE-2026-42875: External Secrets Operator has Namespace Isolation Bypass in CAProvider ConfigMap Resolution for SecretStore

Namespaced SecretStore resources that used CAProvider with type ConfigMap could resolve CA material from another namespace when caProvider.namespace was set. This bypassed the namespace boundary enforced for SecretStore-backed references in providers that rely on the shared runtime CA resolver.

The accessible data is used as CA validation material, hence it is not directly exposed.

Impact:

• Direct data exfiltration risk: low
• Existence disclosure: an attacker can infer whether a target ConfigMap/key exists in another namespace.
• Trust-boundary violation: a tenant can make its SecretStore consume CA material owned by another namespace.