Graham has endured a disappointing stay at the KC Stadium, scoring just once in 20 appearances and it became clear he had become surplus to requirements when Tigers boss Steve Bruce spent B£14million to bring Nikica Jelavic and Shane Long to the club.
That alerted Boro to their former player's availability and they were granted permission to bring him to the Riverside.
A Hull posted on Twitter: "The club has agreed to an early termination of Danny Graham's loan deal from Sunderland.
"The termination of the loan deal allows the striker to join @Boro until the end of the season. We wish Danny all the best."
The Black Cats also confirmed the switch, writing: "Danny Graham has joined @Boro on loan until the end of the season."
Middlesbrough are Graham's fourth club since the start of last season, which he started as a Swansea player.
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- Danny Graham