The bout was reported earlier Thursday by the Las Vegas Review-Journal.
Mir, a two-time UFC titleholder (lineal and interim), has dropped three fights in a row. He was on the receiving end of technical knockouts in two of those losses. In between the TKOs, Mir was roughed up for three rounds by Daniel Cormier during a lopsided unanimous decision.
In his most recent fight, on Saturday at UFC 164, Mir was stopped in the first round by Josh Barnett. Although Mir was being outclassed in the fight, many observers complained afterward that referee Rob Hinds' stoppage at the 1:56 mark came too quickly.
The loss dropped Mir's professional record to 16-8. Despite his recent slide, Mir remains ranked No. 10 among heavyweights by ESPN.com.
Overeem, the former Strikeforce heavyweight champion, has lost two fights in a row -- both by knockout. An opening-round front kick to the chin by Travis Browne on Aug. 17 sent Overeem (36-13 with one no contest) to the canvas. Browne then delivered punches to the face of Overeem, who could no longer defend himself, forcing referee Mario Yamasaki to jump in at the 4:08 mark.