Kearney, 26, was a member of the victorious Irish team which won the 2009 RBS 6 Nations Grand Slam captained by Brian O'Driscoll, who also chipped in with a score against the Blues.
Ireland's top point scorer in this season's Six Nations Jonathan Sexton also kicked 14 points in an excellent performance with the boot.
Welsh 2012 Grand Slam hero Leigh Halfpenny had put the Blues in front with an early penalty but Isa Nacewa also scored for Leinster as they completely overran Cardiff.
Meanwhile, a nerveless kicking display from Greig Laidlaw helped Edinburgh to a historic 19-14 win over Toulouse which means a Scottish side will challenge in the Heineken Cup semi-finals for the first time.
Laidlaw was one of Scotland's standout players in a disappointing RBS 6 Nations campaign and the fly-half further underlined his potential as he scored 14 of Edinburgh's points.
Scotland veteran and their 2008 Six Nations skipper Mike Blair scored Edinburgh's only try of the game to put them ahead early on.
However, Timoci Matanavou's try and three Lionel Beauxis penalties put four-time champions Toulouse in front.
But Laidlaw proved the star of the show as a drop goal and three penalties sealed it for the Scottish side to give Scotland coach Andy Robinson some cheer ahead of a summer tour to Australia and Fiji.