CVE-2022-39257: matrix-org matrix-ios-sdk Improper Authentication

Vulnerability summary

CVE-2022-39257 is a high (CVSS 7.5) Improper Authentication vulnerability in matrix-org matrix-ios-sdk. EPSS estimates a 1.00% chance of exploitation in the next 30 days, higher than 62% of scored vulnerabilities.

Timeline

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

Description

Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, 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-ios-sdk implementing a too permissive key forwarding strategy. The default policy for accepting key forwards has been made more strict in the matrix-ios-sdk version 0.23.19. matrix-ios-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 home server and an attacker, so those who trust their home servers 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.