Logic Error in Matrix Javascript SDK Affects Key Sharing Functionality

CVE-2021-40823

What is CVE-2021-40823?

A logic error present in the room key sharing functionality of the Matrix Javascript SDK prior to version 12.4.1 enables a malicious Matrix homeserver to intercept and steal room encryption keys. This exploitation occurs when a compromised homeserver sends specially crafted Matrix protocol messages to clients participating in an encrypted room, allowing it to decrypt end-to-end encrypted messages intended for those clients. As a result, sensitive communication can be compromised, leading to potential data breaches and privacy violations.

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