The six-foot-five 265-pound lock signed for another season in 2013 with an option for 2014.
Cudmore tweeted he was "very happy and proud" to sign the extension.
"Best club, fans, region in france," he added.
The 33-year-old from Squamish, B.C., joined the club for the 2005-06 season from Grenoble and has made 137 appearances for the top French side.
Dumore, who has played in three World Cups for Canada, co-owns a wine bar/restaurant and sports bar in France.