An exploitable integer overflow vulnerability exists within the MPEG-4 decoding functionality of the GPAC Project on Advanced Content library v1.0.1. The library will actually reuse the parser for atoms with the “stsz� FOURCC code when parsing atoms that use the “stz2� FOURCC code and can cause an integer overflow due to unchecked arithmetic resulting in a heap-based buffer overflow that causes memory corruption. An attacker can convince a user to open a video to trigger this vulnerability.