Cisco Patches Flaw in Webex Videoconferencing App

Cisco has patched a security flaw in its Webex for Windows videoconferencing and messaging software that would have allowed an authenticated attacker to impersonate a legitimate user, download recordings, view or edit meeting information, and steal usernames and other data.

The vulnerability — tracked as CVE-2020-3347 — resulted from what Cisco described as the unsafe use of shared memory in versions of Webex Meetings Desktop App for Windows earlier than 40.6.0. It's one of three flaws in Webex for which the company issued patches this week.

The affected versions of Webex use shared memory to exchange sensitive information such as authentication tokens, usernames, and meeting information with Windows and other applications, the vendor noted. The vulnerability — that a security researcher at Trustwave SpiderLabs recently discovered and reported to Cisco — basically allowed an attacker who already had authenticated access on a system in order to access and retrieve the information from the shared location.

"Malicious users can open and dump contents of this file if they have logon access to the machine," Trustwave said in an advisory on the flaw Thursday. "Simply put, another user can loop over sessions and try to open, read and save interesting contents for future inspection."

Cisco itself rated the vulnerability as being only of medium severity, likely because an attacker would already need to be on a system in order to exploit it. Ilia Kolochenko, founder and CEO of ImmuniWeb, says that fact alone would have severely limited the practical exploitation of flaw. A creative attacker that already had free access to a system would likely not have needed to exploit the Webex flaws to get at the information, he says.

Even so, the flaw represents a failure by the Webex team to follow fundamental software development best practices. "Users that share their machines with third parties should install the available security update without delay," Kolochenko says.

Karl Sigler, senior security research manager at Trustwave's SpiderLabs, says an attacker would not necessarily need to be logged in to a machine directly to take advantage of the Webex flaw. "They could craft malware that when implanted on the victim's system could constantly monitor for Webex tokens," he says. "That would give the attacker access to upcoming meetings, past meetings, and any existing meeting recordings. All of this could leak confidential information to an attacker."

Heightened Risks
The Webex flaw is the latest to highlight what several security researchers have noted is the heightened exposure to data theft and loss that organizations face from the increased use of third-party videoconferencing tools such as Webex, Zoom, and Microsoft Teams by work-from-home employees.

In recent months, security researchers have uncovered relatively serious vulnerabilities in all three platforms even as organizations have been ramping up use of these technologies to support workers forced to work from home because of social-distancing measures.

Earlier this month, for instance, researchers from Cisco Talos discovered two serious vulnerabilities in Zoom, one of which would have allowed attackers to remotely execute code on compromised systems. Security researchers have uncovered multiple other issues with Zoom over the past few months.

Zoom is not the only one with problems. In April, Microsoft scrambled to issue a patch after researchers at CyberArk discovered a flaw in Teams that would have allowed attackers to steal account data using a specially crafted GIF.

Cisco has had its share of issues with Webex as well. Just this week, the company issued patches for two other separately reported security issues in Webex. One of them was an improper input validation error that would have allowed a remote attacker to execute arbitrary code on a vulnerable system (CVE-2020-3263). The second flaw affected a software update feature in Cisco Webex Meetings Desktop App for Mac (CVE-2020-3342) and allowed for remote code execution as well.

Trustwave's Sigler says the takeaway for organizations is to pay closer attention to the collaboration tools they are using. "To minimize your risk, make sure your video [and] messaging solution is kept up to date on patches and make sure that you are using long and strong authentication for both your user accounts and in the actual meetings themselves."

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