Bunn joined Rovers from Northampton last summer but has made only one first-team appearance, in the FA Cup win over non-league Blyth last January.
Bunn is the second Blackburn player to move to the Championship club on loan, and follows winger Keith Treacy to Bramall Lane.
Rovers, meanwhile, have raided Swedish club Malmo for two of their brightest teenage talents.
Strikers Besnik Rustermaj, 16, and Flilip Pivkovski, 15, have both agreed terms at Ewood Park.
Pivkovski enjoyed a successful trial with Rovers in May and now he has agreed his move, and he is joined at Ewood Park by team-mate Rustermaj.
Malmo confirmed that the deal is finalised after they agreed terms with Rovers.