CVE-2023-29529: Matrix JavaScript SDK

Medium severity, CVSS 5.3. EPSS: 0.5% chance of exploitation in the next 30 days.

matrix-js-sdk is the Matrix Client-Server SDK for JavaScript and TypeScript. An attacker present in a room where an MSC3401 group call is taking place can eavesdrop on the video and audio of participants using matrix-js-sdk, without their knowledge. To affected matrix-js-sdk users, the attacker will not appear to be participating in the call. This attack is possible because matrix-js-sdk's group call implementation accepts incoming direct calls from other users, even if they have not yet declared intent to participate in the group call, as a means of resolving a race condition in call setup. Affected versions do not restrict access to the user's outbound media in this case. Legacy 1:1 calls are unaffected. This is fixed in matrix-js-sdk 24.1.0. As a workaround, users may hold group calls in private rooms where only the exact users who are expected to participate in the call are present.

Affected products

• Matrix JavaScript SDK: before 24.1.0 (fixed in 24.1.0)

Published 2023-04-14. Last modified 2026-06-17.