Vulnerability in the Zoom Web Client That Allowed Checking if a Password is Correct for a Meeting
rob_on_earth writes:
[Emphasis in original retained. What appears here is the tl;dr summary; the article provides the steps taken to sleuth this out, as well as a timeline of the researcher's communications with Zoom that started on April 1st. --Ed.]
https://www.tomanthony.co.uk/blog/zoom-security-exploit-crack-private-meeting-passwords/
Zoom meetings were default protected by a 6 digit numeric password, meaning 1 million maximum passwords. I discovered a vulnerability in the Zoom web client that allowed checking if a password is correct for a meeting, due to broken CSRF and no rate limiting.
This enabled an attacker to attempt all 1 million passwords in a matter of minutes and gain access to other people's private (password protected) Zoom meetings.
This also raises the troubling question as to whether others were potentially already using this vulnerability to listen in to other people's calls (e.g. the UK Cabinet Meeting!).
I reported the issue to Zoom, who quickly took the web client offline to fix the problem. They seem to have mitigated it by both requiring a user logs in to join meetings in the web client, and updating default meeting passwords to be non-numeric and longer. Therefore this attack no longer works.
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