DjVuLibre 3.5.27 has a NULL pointer dereference in the function DJVU::filter_fv at IW44EncodeCodec.cpp.
https://www.debian.org/security/2021/dsa-5032
https://usn.ubuntu.com/4198-1/
https://sourceforge.net/p/djvu/bugs/309/
https://lists.debian.org/debian-lts-announce/2021/05/msg00022.html
https://lists.debian.org/debian-lts-announce/2019/11/msg00004.html
http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00069.html
http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00068.html