CVE-2021-42785 : What You Need to Know

A Buffer Overflow vulnerability in tvnviewer.exe of TightVNC Viewer allows remote code execution via a crafted FramebufferUpdate packet.

Understanding CVE-2021-42785

What is CVE-2021-42785?

CVE-2021-42785 is a Buffer Overflow vulnerability in TightVNC Viewer that enables a remote attacker to execute arbitrary code by sending a specially crafted packet from a VNC server.

The Impact of CVE-2021-42785

This vulnerability poses a significant risk as it can be exploited by remote attackers to run malicious code on affected systems, potentially leading to unauthorized access or system compromise.

Technical Details of CVE-2021-42785

Vulnerability Description

The vulnerability exists in tvnviewer.exe in TightVNC Viewer, allowing attackers to execute arbitrary instructions by manipulating FramebufferUpdate packets through a VNC server.

Affected Systems and Versions

Product: TightVNC Viewer
Vendor: GlavSoft LLC
Versions Affected: 2.8.59 and below

Exploitation Mechanism

Remote attackers can exploit this vulnerability by sending a specially crafted FramebufferUpdate packet to the affected TightVNC Viewer, triggering a buffer overflow and executing malicious code.

Mitigation and Prevention

Immediate Steps to Take

Update TightVNC Viewer to version 2.8.60 or higher to patch the vulnerability.
Implement network segmentation to limit exposure of VNC servers to untrusted networks.
Monitor network traffic for any signs of malicious activity.

Long-Term Security Practices

Regularly update software and firmware to ensure systems are protected against known vulnerabilities.
Conduct security training for users on recognizing and reporting suspicious activities.

Patching and Updates

Apply security patches and updates from the official TightVNC Viewer website to address security vulnerabilities and improve overall system security.