Heap-based buffer overflow in the embedded player in multiple RealNetworks products and versions including RealPlayer 10.x, RealOne Player, and Helix Player allows remote malicious servers to cause a denial of service (crash) and possibly execute arbitrary code via a chunked Transfer-Encoding HTTP response in which either (1) the chunk header length is specified as -1, (2) the chunk header with a length that is less than the actual amount of sent data, or (3) a missing chunk header.