TigerVNC version prior to 1.10.1 is vulnerable to heap buffer overflow, which occurs in TightDecoder::FilterGradient. Exploitation of this vulnerability could potentially result into remote code execution. This attack appear to be exploitable via network connectivity.
https://www.openwall.com/lists/oss-security/2019/12/20/2
https://github.com/TigerVNC/tigervnc/releases/tag/v1.10.1
https://github.com/CendioOssman/tigervnc/commit/b4ada8d0c6dac98c8b91fc64d112569a8ae5fb95
http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00039.html