Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Threat Intelligence

05:40 PM
Connect Directly

Cisco Webex Vulns Let 'Ghost' Attendees Spy on Meetings

Three vulnerabilities, patched today, could let an attacker snoop on meetings undetected after the host removes them.

Cisco Webex today patched three vulnerabilities in its videoconferencing platform that could allow an attacker to join meetings as a "ghost" without appearing on the participant list, stay in a meeting after being expelled, and gain access to attendees' data in the meeting room lobby.

Related Content:

Nearly Two Dozen AWS APIs Are Vulnerable to Abuse

The Changing Face of Threat Intelligence

New on The Edge: An Inside Look at an Account Takeover

The vulnerabilities were discovered by IBM Research, where experts decided to analyze the software they were depending on most as employees transitioned to home offices, says Ian Molloy, principal RSM and department head for IBM Research.

"Our CISO recommended looking into best practices around meetings – best ways to protect the company," he says. 

Webex, which is IBM's primary tool for remote meetings, became the research subject. The vulnerabilities they discovered exist in the "handshake" process that Webex uses to create connections between meeting attendees, researchers explained in a writeup of their findings. As part of this process, a client system and server exchange "join" messages with data on meeting attendees, the client application, meeting ID, meeting room details, and other information. 

An attacker with a meeting URL could manipulate the messages between the Webex client application and Webex server back-end to join, and stay in, a meeting without being seen by other attendees. Researchers say they identified the specific pieces of client data that an attacker would need to manipulate to sneak into a Webex meeting undetected.

When a host starts or unlocks a call, an attacker could use the handshake manipulation to slip in unbeknown to attendees. They would be able to see and hear other participants, view shared screens, and chat without revealing their presence. Attendees may hear an extra beep when the extra person sneaks in; other than that, their presence would likely go unnoticed – unless the ghost started to chat with other participants or send messages to the group. 

The Ghost Join flaw (CVE-2020-3419) would let an uninvited guest join a Webex meeting, while a separate vulnerability (CVE-2020-3471) would let them stay after a host kicked them out. The host and other attendees would not see the ghost on a participant list, but they may still listen.

"With increasing back-to-back meetings, this tactic would allow an attacker to listen to more sensitive conversations and could be used in conjunction with social engineering to join locked meetings," researchers wrote, noting once someone becomes a ghost attendee, it's impossible to see them. 

The third vulnerability (CVE-2020-3441) could benefit an attacker before the meeting starts. In the meeting lobby, they could access participant data such as name, email address, IP address, how they connected (phone, browser, Webex Room Kit), and other system details. This data was accessible even if a meeting was locked or hadn't yet started, the researchers noted.

"During the communication protocol, we noticed the participants' name, email, and the IP address are all being collected, even in the lobby," says research scientist Jiyong Jang. "So that means you can potentially collect who might be entering the meeting at this time, and then you can see their location from their IP address." 

This data could be used for further reconnaissance or in more targeted attacks, he adds. The IP address was concerning for employees in home offices, as it revealed the ISP, geolocation, and consumer-grade home network, which are usually less secure than enterprise networks.

"We're not all behind the corporate firewalls and the corporate environments," Molloy says. "We're relying on the security of consumer-grade home routers that your ISP might've given you, where you don't know if everything is as locked down as it should be otherwise."

The researchers were able to demonstrate the "ghost" issue on macOS, Windows, and the iOS version of Webex Meetings applications and Webex Room Kit appliance. Technically, Jang says, it's "not too difficult" to pull off this attack; the tools needed are commonly used at capture-the-flag competitions or among penetration testers, he notes. 

Patches available today should be applied, but the researchers shared some of the workaround they adopted while fixes were in the works. IBM teams began to lock meetings at zero minutes, Molloy says, after which attendees must be manually admitted by the host. He advises watching for external attendees who may seem suspicious or for random phone numbers. 

"We learned which precautions to take. We changed our own internal habits and started locking our meetings down as best we could," Molloy says.

Jang suggests locking meetings with a passcode, which attackers would then also need to exploit these vulnerabilities. IBM teams also began scheduling meetings with unique IDs instead of personal meeting rooms, which are "easily repeatable but easily guessed," Molloy adds.

Kelly Sheridan is the Staff Editor at Dark Reading, where she focuses on cybersecurity news and analysis. She is a business technology journalist who previously reported for InformationWeek, where she covered Microsoft, and Insurance & Technology, where she covered financial ... View Full Bio

Recommended Reading:

Comment  | 
Print  | 
More Insights
Newest First  |  Oldest First  |  Threaded View
FluBot Malware's Rapid Spread May Soon Hit US Phones
Kelly Sheridan, Staff Editor, Dark Reading,  4/28/2021
7 Modern-Day Cybersecurity Realities
Steve Zurier, Contributing Writer,  4/30/2021
How to Secure Employees' Home Wi-Fi Networks
Bert Kashyap, CEO and Co-Founder at SecureW2,  4/28/2021
Register for Dark Reading Newsletters
White Papers
Cartoon Contest
Current Issue
2021 Top Enterprise IT Trends
We've identified the key trends that are poised to impact the IT landscape in 2021. Find out why they're important and how they will affect you today!
Flash Poll
How Enterprises are Developing Secure Applications
How Enterprises are Developing Secure Applications
Recent breaches of third-party apps are driving many organizations to think harder about the security of their off-the-shelf software as they continue to move left in secure software development practices.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
PUBLISHED: 2021-05-05
The “Elementor Addon Elements� WordPress Plugin before 1.11.2 has several widgets that are vulnerable to stored Cross-Site Scripting (XSS) by lower-privileged users such as contributors, all via a similar method.
PUBLISHED: 2021-05-05
The “Livemesh Addons for Elementor� WordPress Plugin before 6.8 has several widgets that are vulnerable to stored Cross-Site Scripting (XSS) by lower-privileged users such as contributors, all via a similar method.
PUBLISHED: 2021-05-05
The “HT Mega – Absolute Addons for Elementor Page Builder� WordPress Plugin before 1.5.7 has several widgets that are vulnerable to stored Cross-Site Scripting (XSS) by ...
PUBLISHED: 2021-05-05
The “WooLentor – WooCommerce Elementor Addons + Builder� WordPress Plugin before 1.8.6 has a widget that is vulnerable to stored Cross-Site Scripting (XSS) by lower-priv...
PUBLISHED: 2021-05-05
The “Elementor Addons – PowerPack Addons for Elementor� WordPress Plugin before 2.3.2 for WordPress has several widgets that are vulnerable to stored Cross-Site Scriptin...