LibVNC before commit 73cb96fec028a576a5a24417b57723b55854ad7b contains heap use-after-free vulnerability in server code of file transfer extension that can result remote code execution
https://www.debian.org/security/2019/dsa-4383
https://usn.ubuntu.com/3877-1/
https://lists.debian.org/debian-lts-announce/2019/10/msg00042.html
https://lists.debian.org/debian-lts-announce/2019/01/msg00029.html