Integer overflow in the vp3_dequant function in the VP3 decoder (vp3.c) in libavcodec in FFmpeg 0.5.x before 0.5.7, 0.6.x before 0.6.4, 0.7.x before 0.7.9, and 0.8.x before 0.8.8; and in Libav 0.5.x before 0.5.6, 0.6.x before 0.6.4, and 0.7.x before 0.7.3 allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted VP3 stream, which triggers a buffer overflow.