CVE-2022-39257 Information

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.

Reference

https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients https://github.com/matrix-org/matrix-ios-sdk/security/advisories/GHSA-qxr3-5jmq-xcf4 https://github.com/matrix-org/matrix-ios-sdk/releases/tag/v0.23.19 https://github.com/matrix-org/matrix-ios-sdk/commit/5ca86c328a5faaab429c240551cb9ca8f0f6262c