CVE-2021-40823

Published: Sep 13, 2021Modified: Jun 17, 2026

5.9

Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Exploitability: 2.2 / Impact: 3.6

Source: NVD

Description

A logic error in the room key sharing functionality of matrix-js-sdk (aka Matrix Javascript SDK) before 12.4.1 allows a malicious Matrix homeserver present in an encrypted room to steal room encryption keys (via crafted Matrix protocol messages) that were originally sent by affected Matrix clients participating in that room. This allows the homeserver to decrypt end-to-end encrypted messages sent by affected clients.

Affected (1)

Products: Matrix: Javascript Sdk

1 product

Configuration A

1 vulnerable

Vulnerable Software	Affected Versions
Matrix Javascript Sdk	Before 12.4.1

Related CWEs

Authentication Bypass by Spoofing

This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.

References (4)

https://github.com/matrix-org/matrix-js-sdk/releases/tag/v12.4.1

Source: cve@mitre.org

Third Party Advisory

https://matrix.org/blog/2021/09/13/vulnerability-disclosure-key-sharing

Source: cve@mitre.org

Vendor Advisory

https://github.com/matrix-org/matrix-js-sdk/releases/tag/v12.4.1

Source: af854a3a-2127-422b-91ae-364da2661108

Third Party Advisory

https://matrix.org/blog/2021/09/13/vulnerability-disclosure-key-sharing

Source: af854a3a-2127-422b-91ae-364da2661108

Vendor Advisory

Timeline

No history available yet.