Celebrity website TMZ.com said the pair were in fear of their lives.
The error briefly saw La La Land named as best picture instead of Moonlight.
On Wednesday it emerged they will not be employed to do the Oscars job again.
But TMZ.com reported that they will not lose their accountancy jobs.
PwC spokeswoman Carey Bodenheimer said that they had been given protection after their home addresses and photos of their families were published in the media.
On Sunday, the team behind La La Land had to be interrupted mid-acceptance speech before the real winner was revealed.
It has been described as the biggest mistake in 89 years of Academy Awards history.
Mr Cullinan mistakenly handed the wrong envelope to the two presenters, Warren Beatty and Faye Dunaway.
They were given the back-up envelope for best actress in a leading role - rather than the envelope which contained the name of the winner for the best film.
PwC counts the votes and organises the envelopes. It has apologised for the mix-up.
Academy President Cheryl Boone Isaacs on Wednesday said that the relationship with PwC was now under review.
Mr Cullinan tweeted a picture of best actress winner Emma Stone minutes before handing the presenters the wrong envelope, and Ms Boone Isaacs blamed "distraction" for the error.
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