TeamViewer issues emergency fix for desktop access vulnerability

The dangerous bug allowed attackers to seize control of PCs through desktop sessions.
Written by Charlie Osborne, Contributing Writer on

TeamViewer has issued an emergency patch to fix a bug which could allow attackers to gain control of other PCs when in desktop sessions.

The vulnerability first came to light on on Monday, when Reddit user xpl0yt told other Redditors to "be careful" after discovering the security flaw. The user linked to a proof-of-concept (PoC) example of an injectable C++ DLL which takes advantage of the bug to change TeamViewer permissions.

The GitHub PoC, uploaded by a user called gellin, describes how the PoC code, tested on TeamViewer x86 Version 13.0.5058, can be utilized to enable the "switch sides" feature that can give a user power over another system involved in a session, which should only be made possible when a user grants that permission manually.

By using naked inline hooking and direct memory modification, in addition, the PoC allows users to harness control of the mouse without paying any attention to control settings and permissions.

TeamViewer acknowledge the bug and pushed out a hotfix to resolve the problem on Tuesday.

Patches for macOS and Linux systems are expected to drop this week, as reported by ThreatPost. Fixes will be delivered automatically.

Speaking to the publication, gellin said both users must be authenticated before the bug can be exploited, and the PoC would need to be deployed using a code mapper or DLL injector.

"Once the code is injected into the process it's programmed to modify the memory values within your own process that enables GUI elements that give you the options to switch control of the session," gellin told the publication. "Once you've made the request to switch controls there are no additional check on the server-side before it grants you access."

In November, TeamViewer announced the launch of TeamViewer 13 with improved remote connection features, reduced CPU loads and new native Linux client supplements.

Best gifts: Top tech gadgets of 2017

Previous and related coverage

    PayPal's TIO Networks reveals data breach impacted 1.6 million users

    The company says evidence of "unauthorized access" has appeared during a recent investigation.

    National Credit Federation leaked US citizen data through unsecured AWS bucket

    Tens of thousands of customers of the credit repair service are believed to be affected.

    HP patches severe code execution bug in enterprise printers

    The vulnerability could be exploited to perform remote code execution.


    A United Airlines pilot made a big speech to passengers. Not everyone will love it

    A United Airlines pilot made a big speech to passengers. Not everyone will love it

    Why you should really stop charging your phone overnight

    Why you should really stop charging your phone overnight

    How to get Photoshop for free
    photoshop free trial

    How to get Photoshop for free

    Photo & Video