Director of football Steve Perryman told BBC Devon: "There is something happening with Ryan which he's entitled to do due to his contract situation.
"He's in talks with another club, we can't reveal anymore details, but we are expecting further updates today."
Harley, who has netted eight goals for the Grecians this term, is out of contract at St James Park in the summer.
The midfielder missed out on both of Exeter's recent trips to Brentford in the league and Johnstone's Paint Trophy, games which both ended in a 1-1 draw.
Source: BBC Sport
Source: BBC Sport