Unpatched Critical Flaw Disclosed in Zoom Software for Windows 7 or Earlier

A zero-day vulnerability has been discovered in Zoom video
conferencing software for Windows that could allow an attacker to
execute arbitrary code on a victim’s computer running Microsoft
Windows 7 or older.

To successfully exploit the zoom vulnerability, all an attacker
needs to do is tricking a Zoom user into performing some typical
action like opening a received document file. No security warning
is triggered or shown to the user at the time of the attack.

The vulnerability has been discovered by a researcher who
reported it to Acros Security, who then reported the flaw to the
Zoom security team earlier today. The researcher wishes to remain
anonymous.

Although the flaw is present in all supported versions of the Zoom
client for Windows, it is only exploitable on systems running
Windows 7 and older Windows systems due to some specific system
characteristics.

“This vulnerability is only exploitable on Windows 7 and earlier
Windows versions. It is likely also exploitable on Windows Server
2008 R2 and earlier though we didn’t test that,” Mitja Kolsek,
0patch co-founder, said in a blog
post^[1] published Thursday.

While Microsoft ended official support for Windows 7 this January
and encouraged users to switch to more secure versions of the
operating system, Windows 7 is still widely used by users and
organizations at large.

Researchers at Acros Security, the creators of 0patch, have
developed a micro patch for all versions of Zoom Client for Windows
(starting with version 5.0.3 and all up to the latest version
5.1.2) to address the security issue and released them to everyone
for free until Zoom Video Communications delivers an official
security patch.

When a user enables 0patch on their system, the malicious code
sent by an attacker doesn’t get executed when a Zoom user clicks on
the “Start Video” button.

“Zoom Client features a fairly persistent auto-update
functionality that is likely to keep home users updated unless they
really don’t want to be,” Kolsek said.

“However, enterprise admins often like to keep control of
updates and may stay a couple of versions behind, especially if no
security bugs were fixed in the latest versions (which is currently
the case).”

Researchers at Acros Security have also developed a working
proof-of-concept exploit for the vulnerability, which they have
shared with Zoom and will not release until the company fixes the
issue.

However, the firm has posted a proof-of-concept video
demonstration that shows how a malicious exploit for this
vulnerability can be triggered by clicking the “start video” button
in the Zoom Client.

No Patch! What should the affected users do?

Until Zoom releases a fix for the issue, users can temporarily stop
using the Zoom client on their older versions of Windows, or update
their OS to a newer version.

Users can also implement micropatch^[2]
released by Acros Security, but since it comes from a third party
software company and not Zoom itself, I would not recommend doing
that.

Due to the ongoing coronavirus outbreak, the use of Zoom video
conferencing software has skyrocketed over the past few months, as
it is being used by not just enterprises but also millions of
regular users across the world to cope with schooling, business,
social engagement, and whatnot.

UPDATE: In a statement provided to The Hacker News,
Zoom confirmed it has now patched the vulnerability mentioned above
with Zoom client version 5.1.3 release.

“Users can help keep themselves secure by applying current
updates or downloading the latest Zoom software with all current
security updates from https://zoom.us/download.”

The ZOOM saga continues…

Just last month, Zoom addressed two critical
vulnerabilities^[3]
in its video conferencing software for Windows, macOS, or Linux
computers that could have allowed attackers to hack into the
systems of group chat participants or an individual recipient
remotely.

In April, a series of
issues^[4] were uncovered and
reported in
Zoom^[5], which raised privacy
and security concerns surrounding the video conferencing software
among millions of its users.

Earlier this year, Zoom also patched a serious privacy
bug in its software that could have allowed uninvited people to
join private meetings and remotely eavesdrop on private audio,
video, and documents shared throughout the session.
^[6]