Kaspersky uncovers 37 vulnerabilities in open-source VNC systems

Kaspersky has presented an analysis of open source Virtual Network Computing (VNC) which uncovered memory corruption vulnerabilities that existed in a substantial number of projects for a significant period of time. According to shodan.io, the exploitation of some detected vulnerabilities could lead to remote code execution affecting the users of VNC systems, which amounts to over 600,000 servers accessible from the global network. 

VNC systems provide remote access to one device from another through the use of remote frame buffer (RFB) protocol. Due to its availability on multiple platforms and presence of multiple open sources, VNC systems have become some of the most popular desktop sharing tools to date. They are actively used in automated industrial facilities enabling remote control of systems, and approximately 32% of industrial network computers having some form of remote administration tools, including VNC.

The prevalence of such systems in general, and particularly ones that are vulnerable, is a significant issue for the industrial sector as potential damages can bring significant losses through disruption of complex production processes. As such, Kaspersky researchers studied some the most popular VNC systems including LibVNC, UltraVNC, TightVNC1.X and TurboVNC.

Although these VNC projects were previously analyzed by other researchers, not all vulnerabilities were uncovered and patched. As a result of Kaspersky’s analysis, 37 CVE records marking various vulnerabilities were created. Vulnerabilities were found not only on the client, but also on the server-side of the system. Some allowed remote code execution, which can then permit a malicious actor to make arbitrary changes on the attacked systems. Alternatively, many server-side vulnerabilities could only be exploited after password authentication, and some servers do not allow password-free access.

“I was surprised to see the simplicity of discovered vulnerabilities, especially considering their significant lifetime,” said Pavel Cheremushkin, Kaspersky ICS CERT vulnerability researcher “This means that attackers could have noticed and taken advantage of the vulnerabilities a long time ago. Moreover, some classes of vulnerabilities are present in many open-source projects and remain there even after refactoring of the codebase, which included vulnerable code. We at Kaspersky believe it is important to systematically detect such multitudes of projects with inherited vulnerabilities, which is why we conduct research of such kind.”

Information on all discovered vulnerabilities have been passed on to the developers. Almost all developers contacted patched the vulnerabilities, with the exception of TightVNC, who do not support this product. The users of the latter should consider alternative VNC system options.

A copy of the report, VNC Vulnerabilities Study, is available on ICS CERT.