The 30-year-old Wales international had fallen out of favour at the Stadium of Light and was been linked with several Championship clubs.
|9/1||Sunderland are 9/1 with William Hill to beat Hull City 1-0|
Vaughan has not featured for the Wearside club since their 3-1 home defeat to Arsenal last month, and appears no closer to the first team under new boss Gus Poyet than recently sacked manager Paolo Di Canio.
The midfielder scored three Premier League goals in 49 appearances for the Black Cats, the most recent coming in a 3-0 win over rivals Newcastle.
Sunderland are currently second from bottom in the Premier League, with only Crystal Palace beneath them, while Nottingham Forest are sat in sixth place in the Championship and pushing for promotion.