The itinerary lasts 1day 9hrs 13min, and has 2 steps, and it will cost 145 euros minimum.

Paris - Vienna
The step from Paris to Vienna lasts 14hrs 53min. You'll travel in a night train from the company ÖBB.
On board, you'll have access to: Drinks and snacks.
You can find tickets from 80 euros.

Vienna - Bucharest
The step from Vienna to Bucharest lasts 18hrs 20min. You'll travel in a night train.
You can find tickets from 65 euros.