The FoFiType1C::cvtGlyph function in fofi/FoFiType1C.cc in Poppler through 0.64.0 allows remote attackers to cause a denial of service (infinite recursion) via a crafted PDF file, as demonstrated by pdftops.
https://usn.ubuntu.com/3647-1/
https://lists.debian.org/debian-lts-announce/2020/07/msg00018.html
https://lists.debian.org/debian-lts-announce/2018/10/msg00024.html
https://access.redhat.com/errata/RHSA-2018:3505