Exeter have signed Jonathan Fortune on a free transfer.
The former Charlton centre-half, 31, left The Valley last summer and has had trials with Leyton Orient and Gillingham.
Fortune has signed a contract until the end of the season at St James Park and is in contention for Saturday's game at MK Dons.
Boss Paul Tisdale made the move with Richard Duffy out for a month after a groin operation and fellow defender Billy Jones missing with a thigh injury.
He said: "Billy is not fit. I hope that's less of a lay-off than Richard's but we saw with Matt Oakley when he pulled his thigh that his recovery, albeit not with us, became chronic when he went back to Leicester. So fingers crossed with Billy and we'll be ultra careful with him.
"Richard is having an operation which puts him out for a month, at least."