After a lengthy hearing on Tuesday, a disciplinary panel found Ashton guilty of biting Waller during Saracens' 27-12 win in the Premiership on Saturday.
Ashton contested two counts of biting, but was found guilty of one and banned for 13 weeks.
He is free to play again on Dec. 19.
"Having considered detailed evidence the panel concluded that during the course of a ruck Chris Ashton bit the arm of Alex Waller at a time that Mr Waller was attempting to clear him out," Philip Evans QC, chairman of the disciplinary panel, said.
"The panel concluded it was a low-end entry point aggravated by his previous record."
Ashton, who has been capped 39 times by England, was banned for 10 weeks earlier this year for eye gouging.
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