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[R2] Zoom Message Spoofing

Critical

Synopsis

Tenable discovered a flaw in Zoom's thick client that allows attackers to hijack control of presenters’ desktops, spoof chat messages, and kick attendees out of Zoom calls. The flaw is due to the lack of message validation. An attacker can spoof Zoom server messages to invoke restricted functionalities reserved for Zoom servers.

In order to successfully exploit this vulnerability the attacker needs know the IP address of an attendee or a Zoom server IP address. Also, the attacker needs to know the attendees meeting attendee IDs, but they can be trivially brute forced.

Because Zoom seems to accept unencrypted UDP messages even when encrypted sessions are enabled, an attacker can exploit this vulnerability without authentication or knowledge of the encryption key.

A full proof of concept can be found in our GitHub repository. A video of the exploit can be found on our blog.

Solution

  • On Windows upgrade to Zoom client 4.1.34814.1119 or later.
  • On Mac OS upgrade to Zoom client 4.1.34801.1116 or later.
  • On Linux upgrade to Zoom client 2.5.146186.1130 or later.

Disclosure Timeline

10/11/2018 - Tenable contacts [email protected] in search of a contact to disclose to.
10/11/2018 - Zoom responded with [email protected] as a valid Security Contact.
10/11/2018 - PGP Request sent to [email protected].
10/11/2018 - Zoom responded with a DropBox link for the disclosure.
10/11/2018 - Full disclosure was uploaded to dropbox. Dropbox account information was attached in this ticket. 90 day set to Jan 9th.
10/11/2018 - Zoom confirmed receipt of the vulnerability.
10/25/2018 - Tenable followed up with Zoom.
10/26/2018 - Zoom responded that issues were fixed and update is pending.
11/07/2018 - Zoom notifies that client will be released soon.
11/20/2018 - Zoom releases fixed version 4.1.34814.1119.
11/29/2018 - Tenable releases an advisory.
11/30/2018 - Zoom releases 2.5.146186.1130 for their Linux client.

All information within TRA advisories is provided “as is”, without warranty of any kind, including the implied warranties of merchantability and fitness for a particular purpose, and with no guarantee of completeness, accuracy, or timeliness. Individuals and organizations are responsible for assessing the impact of any actual or potential security vulnerability.

Tenable takes product security very seriously. If you believe you have found a vulnerability in one of our products, we ask that you please work with us to quickly resolve it in order to protect customers. Tenable believes in responding quickly to such reports, maintaining communication with researchers, and providing a solution in short order.

For more details on submitting vulnerability information, please see our Vulnerability Reporting Guidelines page.

If you have questions or corrections about this advisory, please email [email protected]

Risk Information

CVE ID: CVE-2018-15715
Tenable Advisory ID: TRA-2018-40
Credit:
David Wells
CVSSv2 Base / Temporal Score:
AV:N/AC:L/Au:N/C:P/I:P/A:C
CVSSv2 Vector:
9.0 / 7.0
Nessus Plugin ID: 119241
119242
Affected Products:
Zoom on Windows before version 4.1.34814.1119
Zoom on Mac OS before version 4.1.34801.1116
Zoom on Linux before 2.5.146186.1130
Risk Factor:
Critical

Advisory Timeline

11/29/2018 - [R1] Initial Release
12/03/2018 - [R2] Updated for Linux Release