Ndaw sends St Etienne into League Cup quarters
Elsewhere, Valenciennes and Montpellier ended Ligue 2 participation by beating Boulogne 4-0 and AC Ajaccio 2-0 respectively.
Monaco, in Ligue 1's relegation zone, had something to cheer as they defeated Lorient 5-3 on penalties after the game ended 1-1 following extra-time.
St Etienne, without in-form striker Dimitri Payet through suspension, took only 11 minutes to break through.
Ndaw collected an Emmanuel Riviere cross from the right and curled a fine shot into the top corner.
Bordeaux, who lacked power in midfield in the absence of banned captain Alou Diarra, twice came close to a late equaliser when goalkeeper Jeremie Janot saved well from Jaroslav Plasil and Jussie.
On Wednesday, holders Olympique Marseille visit third division En Avant Guingamp while Olympique Lyon host Paris Saint-Germain.
The draw for the quarter-finals will be made after Wednesday's games.