Kaspersky found dozens of flaws in 4 open-source VNC software

Pierluigi Paganini November 23, 2019

Kaspersky researchers found dozens of flaws in four popular open-source virtual network computing (VNC) systems.

Experts from Kaspersky analyzed several different implementations of a remote access system called Virtual Network Computing (VNC) and identified a number of memory corruption vulnerabilities. Some of the vulnerabilities found by the experts could lead to remote code execution.

The VNC systems provide one device with remote access to another device’s screen, there are implementations major operating systems, including GNU/Linux, Windows, and Android.

VNC is one of the most popular ones, querying shodan.io we can find over 600,000 VNC servers are available online.

VNC systems use the remote frame buffer (RFB) protocol to remotely control a device, transfer screen images, mouse movement and keypress events between devices. 

VNC is widely adopted in industrial environments and many manufacturers of industrial control systems (ICS) leverage on VNC to implement remote control for their products.

Kaspersky has analyzed the popular open-source VNC systems LibVNC, UltraVNC, TightVNC, and TurboVNC.

“As a result of this research, we identified a number of memory corruption vulnerabilities, which have been assigned a total of 37 CVE identifiers. Some of the vulnerabilities identified, if exploited, could lead to remote code execution.” reads the analysis published by Kaspersky.

The experts discovered a total of dozens of vulnerabilities in both server and client software, some of which could be exploited by an attacker to make changes to the targeted system. The experts found 22 security flaws in UltraVNC.

The good news is that most of the 37 vulnerabilities have been already addressed. Experts pointed out that there is a critical issue with the TightVNC because the TightVNC 1.X has been discontinued and maintainers will release no updates.

“All of the bugs are linked to incorrect memory usage. Exploiting them leads only to malfunctions and denial of service — a relatively favorable outcome,” continues Kaspersky. “In more serious cases, attackers can gain unauthorized access to information on the device or release malware into the victim’s system.

Kaspersky experts explained that the exploitation of some of the discovered vulnerabilities poses a serious risk to industrial systems, even if the server-side issues could only exploited by authenticated attackers.

For this reason, experts suggest setting a strong password on the server to mitigate the risks.

Experts explained that client-side apps often include errors in their code that make them vulnerable to hack.

“I was surprised to see the simplicity of discovered vulnerabilities, especially considering their significant lifetime,” said Pavel Cheremushkin, a researcher at Kaspersky ICS CERT. “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.”

Kaspersky published the details of its research on Kaspersky’s ICS-CERT website.

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Pierluigi Paganini

(SecurityAffairs – ICS-SCADA, hacking)

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