The Australian laid down rubber after pulling away from the pits with five minutes of FP1 remaining. He stopped immediately before being pulled back towards the garage.
With such starts being outlawed by the FIA - which demands drivers join the track if they pull away from their pit box - Red Bull immediately realised its error and ordered Webber to join the track.
The team and Webber were summoned to meet the stewards, who elected not to punish them because it had been a mistake.
A statement said: "The team explained that as soon as the error was identified they instructed the driver to drive onto the track without making any changes to the car.
"As all manoeuvres were carried out safely, the stewards accepted these mitigating circumstances."
Marussia's Jules Bianchi also escaped any sanction after entering the pits from outside the entry bollard following a mix-up after first practice.
Rookie duo Valtteri Bottas and Esteban Gutierrez were fined for pit lane speeding offences though.
Bottas had to pay 2800 Euro for being caught doing 73.8 km/h in first free practice, while Gutierrez was fined 800 Euro for doing 63.4 km/h in the afternoon session.
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