Ferron made his move inside the final kilometre to Gap and caught his fellow escapees off guard, with Pierre Rolland (B&B Hotels-KTM) and Warren Barguil (Arkea-Samsic) rounding out the podium.
The 196.4-kilometre stage featured no shortage of attacks ahead of the final weekend in the mountains, but it wasn't until the Cote des Grands that the first break stuck.
KOM leader Rolland was the first to move, followed by Barguil, before Ferron, Andrea Bagioli (Quick-Step Alpha Vinyl), Geoffrey Bouchard (Ag2r Citroën), and Victor Lafay (Cofidis) formed a six-man group.
Despite the best efforts of Trek-Segafredo, Intermarché-Wanty-Gobert Materiaux and BikeExchange-Jayco, the peloton were unable to cut too much into the 2'30" gap with 15 kilometres remaining.
Bagioli looked the fastest of the escapees and it looked as though the Italian would prevail in the final kilometre sprint. Ferron, however, had other ideas; with the TotalEnergies rider darting off the front inside 800 metres and holding off his rivals for a deserved victory.
"It's huge for me," Ferron said of his second pro victory. "We worked hard every day and it's a WorldTour race so this is exceptional for me.
"It's the biggest win of my career. You don't get many chances like this so you have to take them.
"I don't have the best sprint and I knew Bagioli would have the advantage, so when I knew the line was close I just had to go for it - I can't believe I made it."
Wout van Aert's overall lead was not affected by Ferron's efforts, as the Jumbo-Visma star finished less than one minute behind the break to preserve his 1'03" lead over Mattia Cattaneo (Quick-Step Alpha Vinyl).
The Critérium du Dauphiné continues tonight on SBS and SBS On Demand, with coverage of Stage 7 commencing at 10:50pm (AEST).
