Naden, whose place in Penrith's game-day 17 was one of the storylines of grand final week, admitted using the recreational drug to club officials last month.
His positive A-sample for "metabolites of cocaine" was registered in a post-game test conducted by Sport Integrity Australia after the October 25 decider.
Cocaine is prohibited in-competition by both the World Anti-Doping Agency (WADA) and the NRL's Anti Doping Policy, with Naden now serving a provisional suspension as a result.
"Under the Anti-Doping Policy, Mr Naden now has the opportunity to have his B-sample analysed," an NRL statement said.
"The NRL has spoken with Mr Naden and advised him of the support services available to him."
Naden's positive drug test continues a drama-filled 2020 campaign for the late-blooming outside back.
His 12 tries from 18 appearances made for a break-out season as Penrith powered to the grand final.