CVE-2022-39255

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 that legitimately appear to have come from another person, without any indication such as a grey shield. 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. 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. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-ios-sdk version 0.23.19 has been modified to only accept Olm-encrypted to-device messages. Out of caution, several other checks have been audited or added. This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround. To avoid malicious backup attacks, one should not verify one's new logins using emoji/QR verifications methods until patched.

Weakness classification

• security-advisories@github.com: CWE-287
• nvd@nist.gov: CWE-287

Primary references

• security-advisories@github.com — Patch, Third Party Advisory
• security-advisories@github.com — Release Notes, Third Party Advisory
• security-advisories@github.com — Third Party Advisory
• security-advisories@github.com — Vendor Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Patch, Third Party Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Release Notes, Third Party Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Third Party Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Vendor Advisory