Cardiff to face Blackpool in final
An absorbing clash ended 3-2 to Leicester on the night and 3-3 on aggregate and after extra time failed to separate the sides, six penalties were converted before Kermorgant's howler swung the advantage to the Welsh club.
VIDEO: Watch the penalty shootout
Kermorgant (pictured) attempted an audacious dink down the middle of the goal but Cardiff keeper David Marshall, already sprawled on the turf, had time to stick out his arm and claw the ball away.
So weakly hit was the penalty that Kermorgant almost caught up with ball as he followed in.
Martyn Waghorn missed Leicester's next penalty to send the home fans wild as Cardiff set up a play-off final showdown at Wembley on May 22 with Blackpool in a game worth around 90 million pounds - the most lucrative fixture in world football.
Blackpool, who were last in the top flight in 1971, beat Nottingham Forest 4-3 on Tuesday for a 6-4 aggregate victory.