CVE-2024-43803 BMO can expose particularly named secrets from other namespaces via BMH CRD

The Bare Metal Operator (BMO) implements a Kubernetes API for managing bare metal hosts in Metal3. The BareMetalHost (BMH) CRD allows the userData, metaData, and networkData for the provisioned host to be specified as links to Kubernetes Secrets. There are fields for both the Name and Namespace of the Secret, meaning that versions of the baremetal-operator prior to 0.8.0, 0.6.2, and 0.5.2 will read a Secret from any namespace. A user with access to create or edit a BareMetalHost can thus exfiltrate a Secret from another namespace by using it as e.g. the userData for provisioning some host (note that this need not be a real host, it could be a VM somewhere).

BMO will only read a key with the name value (or userData, metaData, or networkData), so that limits the exposure somewhat. value is probably a pretty common key though. Secrets used by other BareMetalHosts in different namespaces are always vulnerable. It is probably relatively unusual for anyone other than cluster administrators to have RBAC access to create/edit a BareMetalHost. This vulnerability is only meaningful, if the cluster has users other than administrators and users’ privileges are limited to their respective namespaces.

The patch prevents BMO from accepting links to Secrets from other namespaces as BMH input. Any BMH configuration is only read from the same namespace only. The problem is patched in BMO releases v0.7.0, v0.6.2 and v0.5.2 and users should upgrade to those versions. Prior upgrading, duplicate the BMC Secrets to the namespace where the corresponding BMH is. After upgrade, remove the old Secrets. As a workaround, an operator can configure BMO RBAC to be namespace scoped for Secrets, instead of cluster scoped, to prevent BMO from accessing Secrets from other namespaces.