Hufanga, who was yellow carded for the incident, was cited by independent citing commissioner Steve Hinds of New Zealand following a review of video footage.
"Having conducted a detailed review of all the evidence available, including all broadcast angles and additional evidence from the player and submissions from his legal representative, the judicial officer upheld the citing," organisers said in a statement on Sunday.
"With respect to the sanction, the offence was deemed to be mid-range (which has an entry point of six weeks).
"However, taking into account mitigating factors and the absence of aggravating factors, the player was suspended for a period of five weeks."
Hufanga, who has 48 hours to appeal, will not be eligible to play again until November 7. Tonga's involvement at the World Cup ended on Saturday despite their upset victory.