Substitute Nicky Forster scored for Hull to force a replay against Middlesbrough after Mark Viduka's opener.
Forster had only been on the pitch three minutes when he headed a 79th-minute David Livermore free-kick past Brad Jones to cancel out Mark Viduka's opener.
The Australian had put the Teessiders ahead with a drilled 73rd-minute shot after seeing Aiyegbeni Yakubu waste two glorious opportunities before the break.
The visitors finally made their Premiership class tell 17 minutes from time when substitute James Morrison's run allowed Yakubu to feed the ball out Viduka, who blasted a low drive past Myhill and into the bottom corner.
But Forster's header opened up the game once again as Myhill saved from Morrison and then tipped a Viduka effort on to the post after Yakubu had fired wide.