Contracts have not yet been signed, but both sides have agreed to the matchup. The 115-pound contest will take place at UFC Fight Night event on ESPN+. The UFC has not yet announced a venue.
Dern, 26, has not fought since May 2018. She gave birth to her first child -- a daughter, Moa -- on June 9. Before the layoff, Dern had built good momentum with wins over Ashley Yoder and Amanda Cooper in a two-month span.
A decorated Brazilian Jiu-Jitsu specialist, Dern is 7-0 since transitioning to MMA in 2016.
Ribas (7-1) is coming off an impressive submission victory over Emily Whitmire in her UFC debut in June. That bout took place at UFC Fight Night in Minneapolis. Ribas, who is from Brazil, trains at American Top Team in Florida.