Pierluigi Paganini
November 30, 2023
Researchers at AppOms discovered a vulnerability in Zoom Room as part of the HackerOne live hacking event H1-4420.
Zoom Rooms is a feature of the Zoom video conferencing platform designed to enhance collaboration in physical meeting spaces, such as conference rooms or huddle rooms. It provides a comprehensive solution for businesses and organizations that want to equip their meeting rooms with video conferencing capabilities.
The experts discovered the vulnerability in June 2023, they warned that an attacker can take over a Zoom Room’s service account and gain access to the victim’s organization’s tenant. The attacker can also have invisible access to confidential information in Team Chat, Whiteboards, and other Zoom applications.
The company promptly addressed the issue and clarified that the vulnerability had no impact on production tenants.
The exploitation of the issue allows threat actors to predict service account email addresses and take over the accounts.
Zoom automatically assigns an email address to any Room service account, it has the format rooms_<account ID>@companydomain.com. The account ID is the user ID value of the service account.
The service account is created with licenses for Whiteboards and Meetings and has extensive access within the tenant.
“The email domain is directly inherited from the user with the Owner role in the tenant at the time of creation – if the Owner has the email address owner@example.com, then the service account will be room_<account ID>@example.com. While there are several ways to leak the account ID within Zoom, simply being in the same meeting as the Room and messaging the Room on Team Chat would disclose the Room’s entire email address.” reads the report published by the company. “The problem with this approach for email generation is that this also applies to email domains of large email providers. For example, if the owner is using an outlook.com email address, the Room’s email address will be room__<account ID>@outlook.com. Since anyone can create an arbitrary Outlook email address, we can create a valid email inbox for a Zoom Room!“
When an attacker creates an arbitrary Outlook email address using the Zoom Room format during the sign-up process, they will receive the activation link. Upon receiving the link, the attacker can click it to activate the account.
The researchers noticed that service accounts cannot be removed from the Team Chat channel feature
“We noted interesting behavior in the Team Chat feature. Zoom provides a feature called Channels, which as the name implies, is a system of text channels. Channels are open to tenant employees by default. Room users were able to view the contents of any channel, including confidential information and persist in this access completely invisibly. Room users could not be removed from the channel by any administrator – even the Owner.” concludes the report. “This finding demonstrated how service accounts could be misused to gain unauthorized access. SaaS systems are composed of many moving parts and managing the security of each part is a difficult task.”
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