CVE 2017-9994
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_
See the 
CVE page on Mitre.org
for more details.
