Substitute Tom Pope headed a 93rd-minute equaliser to lift some of the gloom for troubled Port Vale after James McQuilkin had given Hereford the lead with a stunner.
McQuilkin looked to have settled a game of few chances when he swapped passes with Ryan Green in the 74th minute and drove home an unstoppable 20-yard shot.
But Pope rose at the far post to force a header through the grasp of Hereford goalkeeper Adam Bartlett after fellow substitute Kris Taylor had swung over a free-kick.
Vale, with caretaker manager Mark Grew in charge after Jim Gannon was sacked on Monday, made six changes and Hereford four after both suffered heavy defeats at the weekend.
But the game sprung to life after McQuilkin struck although the visitors will be disappointed not to have hung on for what would have been a ninth away win of the season.