Bradford v Dragons match report
Bradford Bulls (18) 33
T : Lee Gaskell, Jamie Foster 2, Luke Gale, Adrian Purtell
G : Jamie Foster 6
DG : Jamie Foster
Catalans Dragons (16) 20
T : Daryl Millard, Ben Pomeroy, Olivier Elima, Michael Oldfield
G : William Barthau 2
The bottom of the table Bulls, who shipped in a massive 130 points in two games over the Easter period, made an awful start, conceding three tries in the opening 13 minutes.
But, with four players back from injury and illness and bolstered by the midweek loan signing of Jay Pitts from Hull, the home side replied with 30 unanswered points in less than half an hour to turn a 16-0 deficit into a 30-16 lead.
The Dragons, losing finalists in 2007, responded with a try but lost their composure in a frantic attempt to repair the damage allowing the Bulls a place in the last-eight draw for the first time since 2010.
Bradford's Jamie Foster, returning after being taken sick over Easter, claimed two tries in an 20-point personal haul.
The Bulls, five times Challenge Cup winners, welcomed back captain Matt Diskin, Adam Sidlow, making his 150th career appearance, Foster and Luke George, in additon to Pitts.
The Dragons were rocked by the late withdrawal of influential half-back and goal-kicker Thomas Bosc, who limped out of training the day beforehand with a town calf muscle.
But his absence was hardly noticeable at first as the Perpignan side capitalised on early Bradford errors to score three times in 13 minutes to open a 16-0 lead.
However the Yorkshire outfit, so often on the backfoot in recent weeks, regrouped and struck three times themselves in a nine minute spell to go in at half time leading 18-16.
A huge hit deep in Bradford territory from former Bulls star Elliott Whitehead dislodged the ball from the grasp of Jamal Fakir, who travelled in the opposite direction only last month after an acrimonious split with the Dragons, and Daryl Millard scored from the resulting set to give Catalan the lead after just two minutes.
Another handling error from the home side was punished by Ben Pomeroy, before hesitant Bulls defence gifted another ex-Bradford player, Olivier Elima, a third try and the visitors appeared to be cruising into the next round.
But Bradford staged a staggering fightback through quick-fire tries from Lee Gaskell and Foster (two), each converted by Foster to give the Yorkshire outfit a once unlikely two point advantage at the break.
The Bulls then picked up where they left off after the interval and, following a 40-metre break from Tom Olbison, Luke Gale dummied his way through to increase the hosts' advantage.
Now it was the Dragons turn to try and come from behind and both Eloi Pelissier and Zeb Tai were held up by tenacious home defence.
Bradford were not to be denied a place in the quarter-finals, though, and Adrian Purtell scored again for the Bulls, Foster continuing his faultless kicking by adding a conversion and a penalty for a total of six goals.
Michael Oldfield grabbed a try back for the Dragons just after the hour, although William Barthau, deputizing for Bosc, missed two of his four conversion attempts.
Gale put the icing on the cake for Bradford by adding a last minute drop goal.