While ABC News' Elizabeth Vargas was in rehab to treat an admitted addiction to alcohol, her spouse Marc Cohn cheated on her with a mutual friend, gorgeous fitness entrepreneur Ruth Zukerman, Breaking Celebrity News has been told.

“The affair is true, Marc did cheat on her while Elizabeth was in rehab,” a source revealed, insisting that the couple was not separated in 2013, the time of the affair and her rehab treatment.

They are not separated now, the insider added.

“Marc made out he was an angel, standing by his wife while she was in rehab," an insider told the NY Post, which first reported the scandal.

"But meanwhile, he started an affair with" Zukerman, who both he and Vargas made acquaintance with while attending her Flywheel spin classes.

The insider told the paper the dalliance came to light after “a mutual friend spotted Ruth with Marc and called Elizabeth,” with another source close to the situation saying “it was disgusting that he was with Ruth while Elizabeth was in rehab.”

An insider close to Cohn -- who's been married to Vargas for 12 years and has two sons with the ABC journalist -- told the NY Post that something like this was inevitable, as "their marriage has struggled for a lon