CVE-2020-26117 : Vulnerability Insights and Analysis

TigerVNC before 1.11.0 mishandles TLS certificate exceptions, potentially allowing certificate owners to impersonate any server.

Understanding CVE-2020-26117

In rfb/CSecurityTLS.cxx and rfb/CSecurityTLS.java in TigerVNC before 1.11.0, viewers mishandle TLS certificate exceptions, storing them as authorities.

What is CVE-2020-26117?

The vulnerability in TigerVNC allows certificate owners to impersonate servers after a client adds an exception due to mishandling of TLS certificates.

The Impact of CVE-2020-26117

This vulnerability could lead to unauthorized access and potential man-in-the-middle attacks, compromising the integrity and confidentiality of data transmissions.

Technical Details of CVE-2020-26117

TigerVNC before version 1.11.0 is affected by this vulnerability due to mishandling of TLS certificate exceptions.

Vulnerability Description

Viewers in TigerVNC store TLS certificates as authorities, enabling certificate owners to impersonate servers post client exception addition.

Affected Systems and Versions

Product: TigerVNC
Vendor: TigerVNC
Versions affected: All versions before 1.11.0

Exploitation Mechanism

Attackers with a valid TLS certificate could exploit this vulnerability to impersonate servers, potentially leading to unauthorized access.

Mitigation and Prevention

To address CVE-2020-26117, immediate steps and long-term security practices are crucial.

Immediate Steps to Take

Update TigerVNC to version 1.11.0 or later to mitigate the vulnerability.
Monitor for any unauthorized access or unusual server behavior.

Long-Term Security Practices

Regularly update software and apply security patches promptly.
Implement network encryption and strong authentication mechanisms to enhance security.

Patching and Updates

Apply the latest patches and updates provided by TigerVNC to ensure ongoing protection against vulnerabilities.