Napoli, held 0-0 at home by bottom club Chievo in their previous game, took a second-minute lead when Fabian Ruiz turned in Lorenzo Insigne's cross.
Juventus moved on to 40 points, 11 ahead of second-placed Napoli.
Aided by a Davide Biraschi own goal, Napoli came from behind to beat Genoa 2-1.
The result sees Napoli go top of Group C, level on points with Liverpool following their shock 2-0 defeat by Red Star Belgrade earlier Tuesday.
The Italian goalkeeping legend says he is lucky to be able to return to Italy in a Champions League match.
Dries Mertens' hattrick led Napoli to a 5-1 win over Empoli.
When Napoli and Empoli face off in a Serie A match, both teams will probably exhibit playing characteristics instilled by former coach Maurizio Sarri.
According to coach Thomas Tuchel, Gianluigi Buffon will start for Paris Saint-Germain in games against Lille and Napoli.
Dries Mertens' late goal helped Napoli draw 1-1 against AS Roma.
Ángel Di María's goal gave PSG a 2-2 draw against Napoli.
Juve were all set to extend their fine run when Ronaldo put Massimiliano Allegri's men into a first-half lead.
Napoli, Inter Milan, and AC Milan beat Sassuolo, SPAL, and Chievo respectively.
Liverpool coach Jürgen Klopp believes that Liverpool's Champions League loss to Napoli will cause them to play better against Manchester City.
Carlo Ancelotti was not bothered by the fact that it took Napoli almost the whole game to score against Liverpool.
Portuguese superstar Cristiano Ronaldo played a role in all three goals as Massimiliano Allegri's side ensured a maximum 21 points after seven games.
Lorenzo Insigne's two goals helped Napoli beat Torino 3-1 and put Napoli in a tie for the Serie A lead with Juventus.
Red Star last appeared in Europe's premier club competition in 1991-92, the season after they defeated Marseille in the final on penalties in Bari to lift the trophy.
Napoli coach Carlo Ancelotti's tactical adjustments backfired badly.
Liverpool coach Jürgen Klopp is eager to face off against Paris Saint-Germain and Napoli in the Champions League.
Napoli coach Carlo Ancelotti will be going up against AC Milan, the club where he made his name as a coach.
Liverpool registered a convincing 5-0 win over Napoli.
Liverpool coach Jürgen Klopp has confirmed that Alisson will play his first Liverpool game against Napoli.
Bari, who last played in Serie A in 2010-11, finished seventh in Serie B last season and qualified for the promotion playoffs.
The Italian midfielder recently signed for Chelsea from Napoli.