A hole in Apple's iOS for iPhone, iPad and iPod could make the devices vulnerable to remote attackers, warned security firms.
Symantec said that it could be exploited by remote attackers to take complete control of a vulnerable device.
Experts said that the threat, at present, only exists on paper but Apple should issue a fix before it becomes a reality.
Apple said that the company was aware of the report and was investigating.
The problem lies in the way Apple's Mobile Safari handles Adobe Acrobat PDF documents.
As the browser automatically opens PDF files, a hacker could embed malicious code into this file.
Graham Cluley, a computer security expert with Sophos, said that the exploit used the same principle as Jailbreakme --a utility that lets iPhone 4 owners run non-Apple approved applications -- although it uses the exploit in a benign way.
"It uses the same tricks as you do when jailbreaking," the
BBC quoted Cluley as saying.