The Real Madrid footballer intended to delete semi-naked images sent by an admirer, but instead forwarded the snaps to all of his email contacts.
"Cristiano's phone has been buzzing with calls and emails from bewildered pals in the past few days," a source told The Mirror.
"They have all been ringing and messaging to ask what the hell the email is about. And of course they all want to know more about the girl in the pictures. He's had to explain she is just a fan who had sent him some pictures and that he made a mistake by sending them on instead of removing them."
Shayk is said to have dismissed Ronaldo's embarrassing slip-up, as she has come to terms with the amount of female attention that the 26-year-old receives.
"He is embarrassed about the whole thing and is particularly mortified at passing the email on to Irina," the insider added. "But he has done nothing wrong and luckily Irina hasn't confronted him about it.
"Wherever Cristiano goes in the world he gets women throwing themselves at him. And Irina knows dealing with other girls vying for his affection goes with the territory of being on the arm of a footballer like Cristiano.
"He is a bit red-faced about the whole thing and certainly won't make the same mistake again."
Ronaldo, who has a 1-year-old son with a former lover, is reportedly hoping to have a baby daughter with Shayk.