First-half strikes from Nabil Fekir and Tanguy Ndombele put Lyon in control at the Groupama Stadium, and Kasim Nuhu's sending off shortly after the restart left Hoffenheim with a mountain to climb.
But Andrej Kramaric gave the Germans hope, and Kaderabek popped up at the back post to stab in a dramatic leveller in the second minute of added time and extend Hoffenheim's debut group-stage campaign.
"We didn't realise that in a football match, nothing is ever finished," bemoaned Lyon midfielder Lucas Tousart to RMC Sport.
"These are unacceptable errors to make at this level, when you're looking to qualify... It's so annoying to end up with a draw when we had the game in our hands."
Lyon slip three points behind Group F leaders Manchester City -- who thrashed Shakhtar Donetsk 6-0 at the Etihad Stadium -- as they bid to qualify for the last 16 for the first time since the 2011-2012 season.
"We played a good match anyway, even if we don't leave with victory and we are disappointed," said Fekir.
"We must continue with the same state of mind we had before these two goals. There are still two games, nothing is done yet, and it's up to us to learn from this match."
But Julian Nagelsmann's Hoffenheim are now only three points adrift of Lyon in third, and host bottom club Shakhtar at the end of the month.
"At 2-0, Lyon were full of confidence and we had lost all of ours," said 31-year-old coach Nagelsmann. "But, after the red card, for us it was double or quits."
Bizarre opening goal
Lyon took the lead in bizarre circumstances as Ferland Mendy's fierce drive against the post precipitated a frantic goalmouth scramble which ended with Fekir prodding in from just a couple of yards out.
It was a wide open game, much like the 3-3 draw between the teams in Sinsheim two weeks ago, and home goalkeeper Anthony Lopes made a magnificent save from Nico Schulz to deny the visitors an equaliser.
Lyon quickly went up the other end and doubled their advantage as Mendy powered forward again from wing-back and squared for the unmarked Ndombele to slot home with the aid of a big deflection.
It was the 21-year-old France midfielder's second goal in as many games against Hoffenheim, having previously only scored once in his Lyon career.
Florian Grillitsch's long-range strike was just centimetres from giving Nagelsmann's away side a lifeline in the opening minute of the second half, but Kasim was given his marching orders for a second yellow card in the 51st minute.
Lyon missed chances to put the game to bed, though, with Jason Denayer seeing a goal ruled out for offside before Fekir fired straight at Hoffenheim 'keeper Oliver Baumann, and Kramaric set up a tense final quarter of the match with a low 25-yard strike into the bottom corner.
Memphis Depay wasted yet another chance to seal Lyon the three points as his low effort was palmed away by Baumann, and Kaderabek met Joelinton's free-kick in the dying seconds to make Lyon pay for their profligacy.