Weaviate < 1.38.0 - Privilege Escalation via Unchecked Permissions in RBAC Role Assignment

Summary

Weaviate before 1.38.0 does not verify that a principal performing an RBAC role assignment holds the permissions granted by the assigned role. The assignRoleToUser and assignRoleToGroup handlers (POST /authz/users/{id}/assign and /authz/groups/{id}/assign) authorize only that the caller may assign roles to the target user or group, not the permissions contained in the assigned roles, unlike role creation which enforces that a user can only create roles with permissions less than or equal to its own. A user holding only the delegated assign_and_revoke_users or assign_and_revoke_groups permission can assign the built-in admin role, or any high-privilege custom role, to itself or others, escalating to full administrative control of the database.