The West Asians are on the verge of a historic achievement after stunning the highly-fancied Koreans who missed several star players including Park Chu-Young
The Cedars, who were humbled in their opening third round qualifier 6-0 by the Koreans, exacted revenge and boosted their hopes of progressing to the next phase in a thrilling first half against a Taeguk Warriors side who badly missed captain Park Chu-Young.
Ali Al Saadi put Lebanon ahead early, before Koo Ja-Cheol levelled on 21 minutes, only for Abbas Al Atwi to score what proved to be the winner from the spot on 32 minutes.
The result takes Lebanon to 10 points, equal with South Korea, while both sides will eagerly await third-placed Kuwait's game against UAE later in the day.
Kuwait are currently on five points and must win that game to keep their hopes of progressing alive, before they face South Korea away in the final matchday.
Lebanon, though, put themselves in a great position to progress with a famous win which was wildly celebrated by players and fans alike at Beirut's Camille Chamoun Sports City Stadium.
The crowd was cheering from the start, when defender Al Saadi lashed home from close range on four minutes, after Roda Antar's effort was blocked in the box before a set-piece move.
On 12 minutes, Korea had the ball in the back of the net through Lee Keun-Ho however the goal was disallowed for offside.
However, the visitors levelled on 21 minutes, when they won a penalty after Son Heung-Min had inexplicably missed a header from close range only for Lee Keun-Ho to receive a boot to the face in the ensuing scramble.
Wolfsburg midfielder Koo stepped up from the spot and calmly slotted past Lebanon keeper Ziad Al Samad.
However, Koo turned from hero to villain when he clumsily conceded a foul inside the penalty area on 32 minutes, with Cedars striker Atwi converting from 12 yards.
Korea coach Cho Kwang-Rae brought on Ji Dong-Won for Son at the interval in a sign of intent, however the visitors struggled to break down the defensive Lebanon side.
On 65 minutes, Antar came close to settling the game when his header from an Atwi corner cannoned into the woodwork with Korea keeper Jung Sung-Ryong beaten.
Ji fizzed an effort wide from range on 68 minutes but with five minutes to play, Mahmoud El Ali might have wrapped up the result for Lebanon only for his final effort to be tame.
In the end the Koreans failed to create much as Koo fired a late effort out of nothing wide before the hosts celebrated a famous night.
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