The 33-year-old Ireland tighthead appeared before a URC disciplinary panel on Thursday after being cited for an incident during Leinster's 24-18 win over Munster in Dublin.
During the match, Coombes reported the alleged incident to referee Andrew Brace in the first half, but TMO Colin Stanley could not find conclusive video evidence to sanction Furlong.
Furlong was subsequently cited for his actions but avoided suspension after a disciplinary panel unanimously dismissed the complaint, concluding that he had not committed an act of foul play.
"An Independent Disciplinary Committee met today, Thursday, October 29 to consider the Citing Complaint made against Tadhg Furlong of Leinster Rugby as a result of an incident that occurred during the fixture versus Munster Rugby on Saturday, October 24," a statement from the URC read.
"The Citing Commissioner in charge made a complaint about an act of foul play by the Player (Tadhg Furlong No 3) against opponent Gavin Coombes (No 8).
"The Player was cited under Law 9.27 - A player must not do anything that is against the spirit of good sportsmanship including but not limited to grabbing, twisting or squeezing the genitals.
"The Player appeared in front of the Independent Disciplinary Committee, comprising of Simon Thomas (Chair – Wales), Attie Heyns (South Africa) and Pamela Woodman (Scotland), via video conference.
"Having reviewed all of the evidence and considered the submissions in this case, the Independent Disciplinary Committee unanimously concluded that the citing complaint against the Player should be dismissed, on the basis that he did not commit an act of foul play contrary to Law 9.27.
"Notwithstanding the dismissal of the complaint, the Independent Disciplinary Committee found that Munster No 8, Mr Gavin Coombes, had given an honest account of his recollection of events surrounding the incident, and that the Citing Complaint was properly brought before the Independent Disciplinary Committee for determination."
The URC added that a "full written summary explaining the Independent Disciplinary Committee's decision will follow as soon as reasonably practicable."
The decision means that Furlong will be available for selection for Ireland's Nations Championship fixtures against Argentina, Fiji and South Africa, respectively.
Last year, Springbok and Bulls prop Jan-Hendrik Wessels received a nine-match ban for grabbing Josh Murphy's genitals in a URC match despite no video evidence.