LibVNC before commit 4a21bbd097ef7c44bb000c3bd0907f96a10e4ce7 contains null pointer dereference in VNC client code that can result DoS.
ics-cert.kaspersky.com/advisories/klcert-advisories/2018/12/19/klcert-18-034-libvnc-null-pointer-dereference/
lists.debian.org/debian-lts-announce/2018/12/msg00017.html
lists.debian.org/debian-lts-announce/2019/10/msg00042.html
lists.debian.org/debian-lts-announce/2019/11/msg00033.html
security.gentoo.org/glsa/201908-05
security.gentoo.org/glsa/202006-06
usn.ubuntu.com/3877-1/
usn.ubuntu.com/4547-1/
usn.ubuntu.com/4547-2/
usn.ubuntu.com/4587-1/
www.debian.org/security/2019/dsa-4383