Spurs trailed at the break to John O'Shea's first goal for the Black Cats despite having enjoyed the better of a first half during which strike Emmanuel Adebayor hit the bar from just two yards.
However, Carlos Cuellar's own goal three minutes after the restart gave the visitors a foothold, and they took full advantage with 51 minutes gone when Lennon sped through to beat keeper Simon Mignolet.
Adebayor should have put the visitors ahead on the half-hour. Cuellar failed to cut out Jermain Defoe's curling shot, although he took the pace off it to allow Adebayor to get to the loose ball before Mignolet but the strike somehow managed to hit the bar from just two yards.
The home side created their first effort of note seven minutes before the break when Cuellar looped a header over from Adam Johnson's free-kick, and it was they who took the lead two minutes later.
Neither Stephen Fletcher nor O'Shea could make meaningful contact with Sebastian Larsson's free-kick as it sped towards goal, but after the Scot had seen his follow-up blocked by Hugo Lloris, the Republic of Ireland international, back in the starting line-up after illness, gleefully swept the ball into the unguarded net.
There was an element of fortune about Spurs' equaliser when Cuellar headed a 48th-minute corner into his own net, but things went from bad to worse for the home side just three minutes later.
Lennon attempted to lay the ball off, but saw it hit O'Shea and bounce back to his feet, and he raced in on goal to beat Mignolet despite Matt Kilgallon's best efforts to apprehend him.
Spurs should really have ended the game as contest on the hour when, with the Black Cats in disarray, Bale, who was later booked for diving, sprinted from halfway before picking out Defoe in front of goal.
The England striker had time to control before shooting, but as the entire stadium waited for the net to bulge, Mignolet pulled off a breathtaking save he had no right to make to keep his side's hopes alive.
Source: PA
Source: PA