Goals from Nicholas Mwere, old boy Lawrence Tezikya and Ibrahim Mugulusi ended Vipers' unbeaten home run that had stood for over two years.
FUFA Super 8 winners BUL FC were in an unforgiving mood as they beat Uganda Premier League champions Vipers SC 3-2 at the St Mary's Stadium, Kitende, on Friday.
Goals from Nicholas Mwere, old boy Lawrence Tezikya and Ibrahim Mugulusi ended Vipers' unbeaten home run that had stood for over two years.
The last time the Vipers had been beaten at Kitende was in November 2021, 2-0 by URA FC.
Meanwhile, Yunus Sentamu and substitute Mohamed Salem Ekbad netted the hosts' consolation on a night of end-to-end action.
BUL broke the deadlock in the eighth minute through Mwere, who netted after grabbing the pieces left after Vipers scrambled to clear Jerome Kirya's corner.
They added a second at the stroke of half-time, with Tezikya rounding off the backline to squeeze from a tight angle.
The Venoms found a lifeline after 50 minutes through a powerful Sentamu shot past Tom Ikara.
BUL, however, added a third in the 66th minute through substitute Mugulusi, easily beating Fabien Mutombora from outside the box.
Salem then scored Vipers' second through a header off Patrick Mbowa's cross to give his side hope for a late leveller.
However, despite late surges, the BUL backline stood firm as the Vipers succumbed to defeat on home turf.
With the result, BUL have assumed an enormous advantage in the title race as they are on 29 points, five ahead of runners-up Vipers.
While the former will take on Busoga United in the Jinja derby on December 28 in their next match, Vipers will visit Express FC two days later.