CVE-2021-42785: Tightvnc

Critical severity, CVSS 9.8. EPSS: 2.3% chance of exploitation in the next 30 days.

Buffer Overflow vulnerability in tvnviewer.exe of TightVNC Viewer allows a remote attacker to execute arbitrary instructions via a crafted FramebufferUpdate packet from a VNC server.

Affected products

• Tightvnc Tightvnc: up to and including 2.8.59

Published 2021-11-23. Last modified 2026-06-17.