Successful exploits of the flaw would enable attackers to take control of a targeted iPhone, iPad or iPod Touch device, security researchers have found.
The flaw is the way the Apple iOS 4 deals with PDF files and can be exploited if a user can be tricked into visiting a website containing a malicious PDF.
Paul Vlissidis, technical director at IT assurance firm NCC Group, said this type of vulnerability is consistent with what has been seen with new technologies.
"There is always a delay from when they are introduced until new vulnerabilities emerge," he said.
Given the speed with which vulnerabilities are picked up by criminals, it is important for suppliers to issue patches or workarounds quickly, said Vlissidis
Users also need to take responsibility for their own security settings and respond to security alerts from suppliers, he said.
This story was first published by Computer Weekly