User interaction is required to exploit this vulnerability in that the target must open a malicious file.
The specific flaw exists in QuickTimeMPEG.qtx and results when QuickTime attempts to parse a malformed 'genl' atom that may be present in any QuickTime media file. A heap overflow is caused when QuickTime fails to perform proper bounds checking on the amount of data copied to the heap by a set of nested loops which can result in arbitrary code execution.
Patch Availability:
Apple has issued an update to correct this vulnerability. More details can be found at: http://support.apple.com/kb/HT4077