"It is the result of a test carried out by the IOC before the Games. She has admitted to taking a banned substance and was sent home two or three days ago," UCI spokesman Enrico Carpani said.
Baranova was due to take part in the keirin at the Olympics.
"We have been working closely with the IOC and we are very happy with this collaboration, which strengthens our fight against doping," Carpani added.
Baranova, 22, is ranked two in the world in keirin.
A former keirin world champion at junior level, Baranova was a possible medal contender at the London Games.