CVE-2021-42785 Buffer Overflow in tvnviewer.exe via Crafted Packet in TightVNC Viewer 2.8.59

Critical 9.8 Published 23 Nov 2021 Updated 4 Aug 2024

A remote attacker can execute arbitrary code on a victim's machine by sending a crafted packet to the TightVNC Viewer client.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2021-42785?

CVE-2021-42785 is a critical memory corruption vulnerability in GlavSoft LLC TightVNC Viewer, published on 23 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-120

Which versions are affected by CVE-2021-42785?

It affects 1 product.

Products include Tightvnc Tightvnc.

How do I fix CVE-2021-42785?

No fix has been published for CVE-2021-42785 yet. Limit exposure of the affected software until one is available.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2021-42785 being exploited?

There is no known exploitation of CVE-2021-42785 in the wild and no public exploit code.

Sources

Also known as GHSA-7q87-cj95-29mc, UBUNTU-CVE-2021-42785.