The decision has caused protests of All Black favouritism in Wales and South Africa.
Earlier in the tournament, Wallaby Reece Hodge was banned for three games for a tackle on Fiji's Peceli Yato. Like Read, Hodge's tackle wasn't deemed to be a red card on the day but the winger's tackle was referred to a judicial hearing.
The disciplinary committee "deemed that the incident was an act of foul play and warranted a red card in line with the high tackle sanction framework", World Rugby said in a statement.
It added that the tackle was "reckless, rather than deliberate", but contact with the head meant a high degree of danger.
Given Hodge's "exemplary disciplinary record, good character and conduct at the hearing", the committee reduced the six-match entry point by three matches.
In Hodge's case, Fiji was the one who referred the incident to the match's citing commissioner. (Teams have 12 hours post-match to refer any incident – which has passed in the case of the All Blacks.) However, the commissioner also has 36 hours to cite a player themselves for an act of foul play believed to warrant a red card.
