This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of QuickTime Player. 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 occurs when parsing a movie file containing multiple atoms with a different string length. When resizing a buffer in order to make space for the string, the application will forget to include the null-terminator. When the application attempts to null-terminate the string, an out-of-bounds write will occur. If an aggressor can place the a useful heap buffer contiguous to the reallocated string, this can lead to code execution under the context of the applicaiton.