Affected versions of MISP allow authenticated users to retrieve object-reference records by UUID through EventGraphTool::get_reference_data() without first checking whether the requester is authorized to view the object the reference belongs to.
The vulnerable code queried ObjectReference.uuid directly and returned the matching row whenever it existed. Because no parent-object ACL was applied, a user who knew or obtained a reference UUID could retrieve information associated with an object outside their normal access scope. The commit explicitly states that any object reference could be returned by UUID without authorizing its parent object.
The fix retrieves the referenced object's object_id and calls fetchObjectSimple() with the current user. If the user cannot access that parent object, MISP now returns NotFoundException instead of exposing the reference.
Version affected: ≤2.5.45