TightVNC code version 1.3.10 contains null pointer dereference in HandleZlibBPP function, which results Denial of System (DoS). This attack appear to be exploitable via network connectivity.
https://www.openwall.com/lists/oss-security/2018/12/10/5
https://usn.ubuntu.com/4407-1/
https://us-cert.cisa.gov/ics/advisories/icsa-20-343-08
https://lists.debian.org/debian-lts-announce/2019/12/msg00028.html
https://cert-portal.siemens.com/productcert/pdf/ssa-478893.pdf