The Brighton-based former world champion will fight the 25-year-old Welshmen Joe Calzaghe in an interim title bout with the winner to meet the holder, Steve Collins.
The Irishman Collins and the No 1 contender Calzaghe - a southpaw undefeated in 22 fights - were due to meet in Sheffield on 11 October, but the fight has been postponed for the third time after Collins withdrew with a leg injury.
The promoter Frank Warren has instead turned to the 31-year-old Eubank, who was due to fight a light-heavyweight contest on the same bill.
"This fight has been postponed three times now and we've done all we can to accommodate Steve, but we can't go on like this," Warren said.
Eubank will have to shed 6lb to make the 12st weight limit and step down to the super-middleweight division, something which prompted concern from the British Boxing Board of Control.
"We shall be wanting to know what Chris weighs now so we are satisfied he can dehydrate sufficiently to 12 stone to make the weight," John Morris, the BBBC secretary, said.
Eubank, a veteran of 49 contests, the last one in Egypt, does not expect any problems slimming down. "I am 12 stone 6 now so it's not a lot and before I fought Michael Watson for the first time I lost 19lbs," he said, "so I'll do it just by training and going on my usual fruit diet."