The Guinea striker, 20, is yet to appear for Les Gones' first team but spent a profitable year on loan with Troyes in 2012/13.
Yattara spent last season on loan with Angers and scored 11 goals in 30 Ligue 2 appearances. He also scored 3 goals in the Coupe de France.
He has played 9 matches with the Guinea national team, scoring 5 goals.
Yattara has scored in Lyon's 4-2 loss against Debrecen in their first pre-season friendly played on Saturday in Hungary.