The report’s conclusions renew questions about the shadowy world of private hackers for hire. For the right client, or the right sum, such hackers apparently infiltrated the phone of one of the world’s wealthiest and most powerful men. The report did not say which private cybersecurity company was used, but suggested that the Tel Aviv-based NSO Group and Milan-based Hacking Team had the capabilities for such an attack.

Image Some of the texts that Mr. Bezos exchanged with Saudi Arabia’s crown prince, Mohammed bin Salman, on WhatsApp. Credit... via FTI

The hack also exposed how popular messaging platforms like WhatsApp have vulnerabilities that attackers can exploit. In October, WhatsApp sued the NSO Group in federal court, claiming that NSO’s spy technology was used on its service to target journalists and human rights activists. WhatsApp, which is owned by Facebook, has patched the flaw that the malware used.

“This case really highlights the threats that are posed by a lawless and unaccountable private surveillance industry,” said David Kaye, the United Nations special rapporteur who was a co-author of Wednesday’s statement. “The companies who are creating these tools are extremely crafty and aggressive, and it’s a cat-and-mouse game at this point.”

NSO said it was not involved in any hack of Mr. Bezos’ phone. Hacking Team did not respond to a request for comment. WhatsApp declined to comment, as did FTI Consulting, the company that Mr. Bezos’ security team hired to examine his phone and that wrote the forensic analysis. Amazon declined to comment on behalf of Mr. Bezos.

Malware that was created for the explicit purpose of prying into private online communications, also known as spyware, has become a $1 billion industry. While companies like the NSO Group and Hacking Team have been accused of deploying their spyware with governments to monitor dissidents and others, smaller companies also sell simpler versions of the software for as little as $10, allowing people to snoop on their spouses or children.

Ron Deibert, the director of Citizen Lab at the University of Toronto, which was not involved in the Bezos investigation, said the Amazon chief’s situation was “a reminder that the proliferation of commercial spyware is a global security problem for all sectors, from government and businesses to civil society.”

Over the years that he has run Amazon, Mr. Bezos has largely kept private. That changed when The National Enquirer published photos and messages last year between him and Ms. Sanchez, a TV anchor. Mr. Bezos and his wife, MacKenzie Bezos, later got a divorce.