The DecodeNumber function in unrarlib.c in unrar 0.0.1 (aka unrar-free or unrar-gpl) suffers from a NULL pointer dereference flaw triggered by a crafted RAR archive. NOTE: this may be the same as one of the several test cases in the CVE-2017-11189 references.
https://lists.debian.org/debian-lts-announce/2021/02/msg00026.html