CVE-2021-21842

An exploitable integer overflow vulnerability exists within the MPEG-4
decoding functionality of the GPAC Project on Advanced Content library
v1.0.1. A specially crafted MPEG-4 input can cause an integer overflow when
processing an atom using the ‘ssix’ FOURCC code, 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.