This vulnerability allows local attackers to execute arbitrary code on vulnerable installations of Apple OS X. 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 the AppleUpstreamUserClient kernel extension. The issue lies in the failure to validate the size of a buffer prior to accessing it. An attacker can leverage this vulnerability to execute code within the context of the kernel.