TeamViewer hurries to fix desktop access vulnerability

TeamViewer Permissions bug can be exploited to take over computers during active sessions

TeamViewer hurries to release a fix for system vulnerability which could allow hackers to control computers during desktop sessions^[1]. The Permissions bug was first discovered on Monday when the Reddit user named xpl0yt informed about the vulnerability by showing how a proof of concept injectable C++ DLL can be used to modify TeamViewer permissions.

The bug can affect TeamViewer x86 Version 13.0.505 on MacOS, Windows and Linux operating systems. TeamViewer has admitted that they are aware of the system vulnerability and released a patch for Windows on Tuesday^[2]. According to senior PR manager, Alex Schmidt, a fix for Linux and MacOS versions should be issued on late Tuesday or Wednesday.

This TeamViewer vulnerability is a potential threat to numerous companies and private users since this application allows to share the desktop screen or transfer files from the local to a remote computer. By taking over the control during active sessions, crooks are able to control the mouse of the PC without permission.

The bug uses direct memory alteration and naked inline hooking to modify TeamViewer permissions

On GitHub, the user named Gellin explains that the proof of concept injectable C++ DLL employs pattern scanning to identify key parts in the code which hold pointers by assembly registers^[3]. Additionally, Gellin mentions the following:

It applies inline naked hooks a.k.a code caves, to hi-jack the pointers to use for modification via direct memory access to their reversed classes.

The proof of concept code can be used to enable “switch sides” feature to control the viewer's computer without consent^[4]. Originally, to do so, you have to get the approval of both, the local and the remote computer. However, TeamViewer vulnerability can be exploited using DLL injector, Manual Mapper, and PE Loader.

TeamViewer bug might be leveraged by Tech Support scammers

Security Researcher from ASERT, Nelson, says that typically, criminals take advantage of these types of bugs quickly until they are fixed^[5]. He also adds that Tech Support scammers might benefit from TeamViewer vulnerability the most:

This bug will be of particular interest to attackers carrying out malicious tech support scams. Attacker will no longer need to trick the victim into giving control of the system or running malicious software, instead they will be able to use this bug to gain access themselves.

It is vital to be aware of the TeamViewer bug, since malevolent people might damage your computer or steal private data, including credentials. Experts warn to stay safe and take precautionary measures until you receive an update to fix Permissions bug.