CVE-2022-39249: matrix-org matrix-js-sdk Improper Authentication

Vulnerability summary

CVE-2022-39249 is a high (CVSS 7.5) Improper Authentication vulnerability in matrix-org matrix-js-sdk. EPSS estimates a 1.28% chance of exploitation in the next 30 days, higher than 69.5% of scored vulnerabilities.

Timeline

1. 28-09-2022
   PublishedVulnerability first disclosed.
2. 23-04-2025
   Last modifiedVulnerability information updated.

Description

Matrix Javascript SDK is the Matrix Client-Server SDK for JavaScript. Prior to version 19.7.0, an attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others. This attack is possible due to the matrix-js-sdk implementing a too permissive key forwarding strategy on the receiving end. Starting with version 19.7.0, the default policy for accepting key forwards has been made more strict in the matrix-js-sdk. matrix-js-sdk will now only accept forwarded keys in response to previously issued requests and only from own, verified devices. The SDK now sets a `trusted` flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with `trusted = false` are decorated appropriately, for example, by showing a warning for such messages. This attack requires coordination between a malicious homeserver and an attacker, and those who trust your homeservers do not need a workaround.

• CWE-287Improper AuthenticationWhen an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
• CWE-322Key Exchange without Entity AuthenticationThe product performs a key exchange with an actor without verifying the identity of that actor.