Dunning, 25, is 17-13 with a 2.74 ERA and 300 strikeouts in 49 career starts in three minor-league seasons (20016-18). He has limited opponents to a .229 average with a 1.13 WHIP.
He was a first-round pick of the Washington Nationals in 2016 and was traded to the Sox along with Lucas Giolito and Reynaldo Lopez for outfielder Adam Eaton that December.
The Sox made three more roster moves, reinstating outfielder Adam Engel from the injured list, designating infielder Cheslor Cuthbert for assignment and optioning pitcher Jose Ruiz to Schaumburg.