An issue was discovered in libvncserver-0.9.12. There is a divide by zero in rfbSendRectEncodingRaw function in libvncserver/rfbserver.c.
Attackers can launch a denial of service attack by sending a special message to the VNC server.
Name: Kailong Zhu, Hui Huang, Lu Yu
Created libvncserver tracking bugs for this issue:
Affects: epel-7 [bug 1896740]
NOTE: at least one commercial firewall has flagged TurboVNC connections as vulnerable to this CVE, but to the best of my knowledge and testing, LibVNCServer is the only TightVNC-compatible code base that is (was) vulnerable. I was unable to reproduce the vulnerability with TightVNC 1.3.x, TigerVNC, or TurboVNC. Refer to https://github.com/TurboVNC/turbovnc/pull/273#issuecomment-784498698.
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):
This issue has been addressed in the following products:
Red Hat Enterprise Linux 8
Via RHSA-2021:1811 https://access.redhat.com/errata/RHSA-2021:1811