In line libavcodec/h264dec.c:500 in libav(v13_dev0), ffmpeg(n3.4), chromium(56 prior Feb 13, 2017), the return value of init_get_bits is ignored and get_ue_golomb(&gb) is called on an uninitialized get_bits context, which causes a NULL deref exception.
https://lists.ffmpeg.org/pipermail/ffmpeg-cvslog/2017-January/104221.html
https://lists.debian.org/debian-lts-announce/2019/03/msg00041.html