This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Apple QuickTime. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
The specific flaw exists within the handling of H.263 data. The H.263 data is not properly validated which can result in writing past an intended buffer. By abusing this behavior an attacker can ensure this memory is under control and leverage the situation to achieve remote code execution under the context of the user currently logged in.