BigBlueButton is an open‑source virtual classroom platform. In versions 3.0.19 and earlier, when a participant joins a meeting with the microphone muted, the client erroneously continues to transmit audio to the server until the participant unmutes. The server discards the received media, so it is not played to other attendees, but a malicious or compromised server may capture and analyze the audio stream. The primary consequence is the potential exposure of private conversation data to anyone controlling or observing the server environment. This vulnerability is classified as CWE‑200, an information exposure weakness.

The affected product is BigBlueButton, version 3.0.19 or earlier. The issue was identified in the source code at the commit referenced in the advisory and was fixed in BigBlueButton v3.0.20, as noted in the official security advisory.

The vulnerability carries a low CVSS score of 2 and an EPSS below 1 %, indicating a small probability of exploitation under current conditions. It is not present in the CISA KEV catalog, further suggesting limited exposure. Exploitation requires a malicious or compromised server operator; remote attackers cannot capture audio from a muted participant without controlling the server. Consequently, the risk is confined to compromised server administrators or attackers who have remote control of a BigBlueButton deployment.