The Google Project Zero researcher found a bug in XML parsing on the Zoom client and server.

Zoom patched a medium-severity flaw, advising Windows, macOS, iOS and Android users to update their client software to version 5.10.0.

The Google Project Zero security researcher Ivan Fratric noted in a report that an attacker can exploit a victim’s machine over a zoom chat. The bug, tracked as CVE-2022-22787, has a CVSS severity rating of 5.9.

“User interaction is not required for a successful attack. The only ability an attacker needs is to be able to send messages to the victim over Zoom chat over XMPP protocol,” Ivan explained.

So called zero-click attacks do not require users take any action and are especially potent given even the most tech-savvy of users can fall prey to them.

, Zoom Patches ‘Zero-Click’ RCE Bug, The Cyber Post

XMPP stands for Extensible Messaging Presence Protocol and is used to send XML elements called stanzas over a stream connection to exchange messages and presence information in real-time. This messaging protocol is used by Zoom for its chat functionality.

In a security bulletin published by Zoom, the CVE-2022-22786 (CVSS score 7.5) affects the Windows users, while the other CVE-2022-22784, CVE-2022-22785, and CVE-2022-22787 impacted Zoom client versions before 5.10.0 running on Android, iOS, Linux, macOS, and Windows systems.

Working of Bug  

The initial vulnerability described by Ivan as  “XMPP stanza smuggling” abuses the parsing inconsistencies between XML parser in Zoom client and server software to “smuggle” arbitrary XMPP stanzas to the victim machine.

An attacker sending a specially crafted control stanza can force the victim client to connect with a malicious server thus leading to a variety of attacks from spoofing messages to sending control messages.

Ivan noted that “the most impactful vector” in XMPP stanza smuggling vulnerability is an exploit of “ClusterSwitch task in the Zoom client, with an attacker-controlled “web domain” as a parameter”.