You need to provide more information for that determination.
What is the whole paragraph this sentence is used in? What is the paragraph prior to this sentence? What is the sentence after this one?
Has or had could be correct in either case, depending on the usage.
If you are saying that it has been under control in the past, and it can be again in the future.
Or you are saying it had been under control in the past, however now it is uncontrollable.
Student or Learner