{"id":"GHSA-r48r-j8fx-mq2c","summary":"matrix-js-sdk subject to user spoofing via Olm/Megolm protocol confusion","details":"### Impact\n\nAn 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.\n\nAdditionally, 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.\n\nThese attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm.\n\n### Patches\n\nmatrix-js-sdk has been modified to only accept Olm-encrypted to-device messages.\n\nOut of caution, several other checks have been audited or added:\n- Cleartext `m.room_key`, `m.forwarded_room_key` and `m.secret.send` to_device messages are discarded.\n- Secrets received from untrusted devices are discarded.\n- Key backups are only usable if they have a valid signature from a trusted device (no more local trust, or trust-on-decrypt).\n- The origin of a to-device message should only be determined by observing the Olm session which managed to decrypt the message, and not by using claimed sender_key, user_id, or any other fields controllable by the homeserver.\n\n### Workarounds\n\nAs this attack requires coordination between a malicious home server and an attacker, if you trust your home server no particular workaround is needed. Notice that the backup spoofing attack is a particularly sophisticated targeted attack.\n\nWe are not aware of this attack being used in the wild, though specifying a false positive-free way of noticing malicious key backups key is challenging.\n\nAs an abundance of caution, to avoid malicious backup attacks, you should not verify your new logins using emoji/QR verifications methods until patched. Prefer verifying with your security passphrase instead.\n\n### References\nBlog post: https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients\n\n### For more information\nIf you have any questions or comments about this advisory, e-mail us at [security@matrix.org](mailto:security@matrix.org).\n","aliases":["CVE-2022-39251"],"modified":"2023-11-01T04:59:47.586508Z","published":"2022-09-30T00:41:24Z","database_specific":{"nvd_published_at":"2022-09-28T20:15:00Z","cwe_ids":["CWE-287","CWE-322"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2022-09-30T00:41:24Z"},"references":[{"type":"WEB","url":"https://github.com/matrix-org/matrix-js-sdk/security/advisories/GHSA-r48r-j8fx-mq2c"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2022-39251"},{"type":"WEB","url":"https://github.com/matrix-org/matrix-js-sdk/commit/a587d7c36026fe1fcf93dfff63588abee359be76"},{"type":"PACKAGE","url":"https://github.com/matrix-org/matrix-js-sdk"},{"type":"WEB","url":"https://github.com/matrix-org/matrix-js-sdk/releases/tag/v19.7.0"},{"type":"WEB","url":"https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients"},{"type":"WEB","url":"https://security.gentoo.org/glsa/202210-35"}],"affected":[{"package":{"name":"matrix-js-sdk","ecosystem":"npm","purl":"pkg:npm/matrix-js-sdk"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"19.7.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2022/09/GHSA-r48r-j8fx-mq2c/GHSA-r48r-j8fx-mq2c.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N"}]}