Well if use the wikipedia definition
(From the first paragraph)
is a plot device whereby a seemingly unsolvable problem is suddenly and abruptly resolved, with the contrived and unexpected intervention of some new event, character, ability, or object.
Wormhole aliens, already established
Wormhole aliens haveing control of the wormhole, alread establsihed
I.e not new so it fails at least some of the criteria of a Dues Ex Machina.