libavcodec/webp.c in FFmpeg before 2.8.12 3.0.x before 3.0.8 3.1.x before 3.1.8 3.2.x before 3.2.5 and 3.3.x before 3.3.1 does not ensure that pix_fmt is set which allows remote attackers to cause a denial of service (heap-based buffer overflow and application crash) or possibly have unspecified other impact via a crafted file related to the vp8_decode_mb_row_no_filter and pred8x8_128_dc_8_c functions.