A late goal from substitute striker Glenn Murray, his first in four months, finished off Kidderminster's dogged resistance and earned Carlisle a place in the Northern Section final of the LDV Vans Trophy with a 1-0 win.
The visitors looked to have survived a massive barrage by the Cumbrians until the 87th minute when Chris Billy, United's best midfielder on the night, slipped the ball through for Murray to run on and slam a low shot past keeper John Danby.
Murray had replaced an off-key Derek Holmes on the hour and almost made his mark within a few minutes of coming on when he missed an inviting cross from debutant Mark Rivers by inches as he flung himself full length.
Carlisle dominated the game against unenterprising opponents who defended with determination but rarely threatened as an attacking force. In fact, Carlisle had half a dozen good chances in the opening half hour when it was one-way traffic towards the Harriers goal.
Karl Hawley, United's leading scorer turned provider for Holmes, who mis-kicked from six-yards and Danby had to be on his metal to save a Billy pile-driver on 37 minutes.
It took the visitors until the 39th minute to seriously trouble the home defence and then goalkeeper Keiren Westwood was alert to the threat, producing a fine reaction save from Simon Russell's low shot.
Carlisle piled on the pressure after the break without being able to break Harriers stubborn resistance and John Mullins looked fortunate to get away with a handball appeal when Zigor Aranalde drove the ball into the box.
Substitute Simon Hackney almost broke the deadlock with a stinging effort which Danby turned away for a corner but just when extra time beckoned, Murray stepped in with the decisive strike.