Simon Mignolet's error gave the Bulgarians an early lead before Rickie Lambert and Jordan Henderson turned it around but a late equaliser denied the Reds a morale-boosting win
The Bulgarian side took a shock lead in just the third minute when a disastrous Simon Mignolet error allowed Dani Abalo to pounce and score but Rickie Lambert took advantage of some similarly dreadful home defending to equalise only five minutes later for his first European goal.
Raheem Sterling then broke free to cross for Jordan Henderson to give the Reds the lead before half-time but Brendan Rodgers's side switched off at the death when Georgi Terziev scored from a corner.
Liverpool now need to beat Basel in their final group game if they are to reach the knockout stages.
Yet seeming to show pity on their beleaguered opponents, Ludogorets gifted Liverpool a way back into the game five minutes later. Lambert was the beneficiary, capitalising on indecision in the defence to nod beyond onrushing goalkeeper Vladislav Stoyanov and into the corner.
The Bulgarians responded impressively, however, as they continued to press forward with confidence. An error-strewn game nearly brought another costly one as Kolo Toure turned Abalo's cross narrowly past his own post.
But Liverpool regrouped thereafter and took the lead thanks to a superbly worked goal eight minutes before half-time. Sterling was the architect, sending a pinpoint low cross to the far post - where Henderson burst in and expertly lobbed Stoyanov.
Ludogorets were not able to begin the second half how they did the first, although they enjoyed the majority of the possession. Espinho had the best chance of the early exchanges, curling a 20-yard free kick harmlessly over the crossbar.
Liverpool continued to invite pressure, though, with Marcelinho's long-range effort deflected just wide off Joe Allen.
There was a palpable sense of tension in the Reds' play as the final whistle drew closer, especially when Sterling hit straight at Stoyanov when one-on-one with the shot-stopper.
And that miss was to prove incredibly costly as Svetoslav Dyakov flicked on a corner to leave Terziev with an easy task and heap further misery on Rodgers.