![]() ![]() Matrix Javascript SDK is the Matrix Client-Server SDK for JavaScript. To avoid malicious backup attacks, one should not verify one's new logins using emoji/QR verifications methods until patched. This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround. Out of caution, several other checks have been audited or added. matrix-ios-sdk version 0.23.19 has been modified to only accept Olm-encrypted to-device messages. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. This can allow, for example, to inject the key backup secret during a self-verification, to make a targeted device start using a malicious key backup spoofed by the homeserver. Additionally, a sophisticated attacker cooperating with a malicious homeserver could employ this vulnerability to perform a targeted attack in order to send fake to-device messages appearing to originate from another user. ![]() Prior to version 0.23.19, an attacker cooperating with a malicious homeserver can construct messages that legitimately appear to have come from another person, without any indication such as a grey shield. Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. As this attack requires coordination between a malicious homeserver and an attacker, those who trust their homeservers do not need a particular workaround. An additional check has been made to report an error when one of the device ID matches a cross-signing key. Starting with version 19.7.0, the matrix-js-sdk has been modified to double check that the key signed is the one that was verified instead of just referencing the key by ID. Even though the attack is partly made possible due to the design decision of treating cross-signing user identities as Matrix devices on the server side (with their device ID set to the public part of the user identity key), no other examined implementations were vulnerable. ![]() The vulnerability is a bug in the matrix-js-sdk, caused by checking and signing user identities and devices in two separate steps, and inadequately fixing the keys to be signed between those steps. This would lead to the other device trusting/verifying the user identity under the control of the homeserver instead of the intended one. ![]() Prior to version 19.7.0, an attacker cooperating with a malicious homeserver could interfere with the verification flow between two users, injecting its own cross-signing user identity in place of one of the users’ identities. Matrix JavaScript SDK is the Matrix Client-Server software development kit (SDK) for JavaScript. ![]()
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