Carmen Electra -- Double Dipping Tongues with Ex-Husband Dave Navarro

Carmen Electra stuck her tongue in a warm, familiar place last night ... Dave Navarro's mouth -- and the exes weren't shy about it.

They were walking into a hard rock award show in downtown L.A. when they took a moist selfie, which Dave tweeted, saying ... "May get lucky with one tonight."

Carmen and Dave divorced in 2007 after 3 and a half years of marriage ... and a reality show.

Who says you can't go back?

Based on how Carmen looks in this video -- we definitely get it, Dave.