Cisco Webex & Zoom Bug Lets Attackers Spy on Conference Calls

Researchers have discovered a vulnerability in the Zoom and Cisco Webex conference platforms that could let an attacker scan for and drop into video meetings unprotected with a password.

The "Prying-Eye" vulnerability was discovered in July by researchers with the CQ Prime Threat Research Team, a division of application security startup Cequence. Cisco and Zoom were immediately notified of the flaw, and both companies have issued patches for their systems.

An adversary could exploit Prying-Eye to launch an enumeration attack, which leverages automation to detect numeric or alphanumeric sequences that are used as identifiers for public-facing applications. CQ Prime analysts targeted the web conferencing APIs with a bot designed to scan and discover valid numeric meeting IDs for Webex and Zoom calls. If the meeting isn't protected with a password or other authentication, the attacker could drop in.

When the bot cycles through the sequences to find a valid ID, it comes back and determines whether the ID is valid and whether it requires a password, says Shreyans Mehta, co-founder and CTO of Cequence and leader of this research. An attacker could respond back and view or listen to an active meeting, and could also use this tactic to determine the IDs of future calls.

That's not all the attacker could discover, Mehta points out. "Once you identify an unprotected meeting ID, you can get more information about that meeting host and you can get information about who owns the meeting identifier," he explains. Depending on the target, the attacker could gain access to the meeting host's name or email address in addition to information about the meeting.

It is worth noting the intruder may be noticed, as callers are announced when they join meetings. There is no indication this vulnerability has been exploited on either Webex or Zoom platforms.

When Cisco learned an attacker could abuse Webex API calls to enumerate meeting numbers, it created a fix and issued an advisory to warn users of the bug. It advises admins keep the default configuration, which requires the use of a password when a meeting is created. Webex offers a randomly generated password by default in the meeting setup process for sites that don't mandate password protection; however, users can replace this password with their own or disable password protection if the site allows.

Zoom is releasing new controls for its meeting and webinar password settings. Before today's update, users could enable passwords on a meeting-by-meeting basis; this change adds new settings at the account, group, and user level. Passwords can now be required for scheduling new meetings, setting up instant meetings, and for personal meeting ID (PMI). The additional settings are meant to give account owners and admins more control over meeting passwords.

New password settings were enabled by default for accounts without Zoom Rooms on September 29. They will be enabled by default for accounts with Zoom Rooms on November 23. This change will not affect users who join calls by clicking a meeting link or through desktop calendar integration.

The idea behind this research was not only to highlight the vulnerability in Cisco and Webex but to draw attention to the danger of enumeration attacks and how they can target APIs, says Mehta. Many of the applications in use today tie web forms or mobile devices to back-end systems. In addition to unauthorized access, an enumeration attack could be used as an application distributed denial-of-service attack and cycle ongoing requests until the application shuts down, driving up infrastructure cost.

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