According to a report on Gizmodo, anyone can bypass the security code on an iPhone by pressing a series of buttons on the device.
You have to begin the shutdown procedure, and interrupt that with an emergency call, followed by the off button and Cancel.
According to the report, this will boot the iPhone into the full phone application, giving a user unauthorised access to the device.
The latest version of the iPhone has been under some pressure despite healthy sales for Apple.
The company was criticised over its Maps application and some users have complained that the battery of the iPhone 5 is not up to scratch.
There were also initial complaints that a purple haze was observed on pictures taken with the camera in bright light.
Apple recently updated the operating system to remedy some of the shortcomings.