{"id":"CVE-2022-39248","aliases":["EUVD-2022-6804","GHSA-fpgf-pjjv-2qgm"],"status":"published","title":"matrix-android-sdk2 vulnerable to Olm/Megolm protocol confusion","description":"matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, 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. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-android-sdk2 version 1.5.1 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption. 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.","severity":{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00996,"percentile":0.62933,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-287","CWE-322"],"published":"2022-09-28T20:05:12Z","modified":"2026-10-28T02:30:28Z","fixes":[{"ecosystem":"Maven","package":"org.matrix.android:matrix-android-sdk2","fixed_in":["1.5.1"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Maven","package":"org.matrix.android:matrix-android-sdk2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"1.4.36"},{"fixed":"1.5.1"}]}]},{"source":"osv","ecosystem":"Maven","package":"org.matrix.android:matrix-android-sdk2","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.5.1"}]}],"versions":["0.0.2","1.2.1","1.2.2","1.3.0","1.3.10","1.3.13","1.3.14","1.3.18","1.3.2","1.3.4","1.3.7","1.3.8","1.3.9","1.4.11","1.4.13","1.4.14","1.4.16","1.4.2","1.4.25","1.4.27","1.4.32","1.4.34","1.4.36","1.4.4"]}],"products":[{"vendor":"matrix","product":"software_development_kit"},{"vendor":"matrix-org","product":"matrix-android-sdk2"}],"references":[{"url":"https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients","tags":["x_refsource_MISC","x_transferred","Vendor Advisory","article","web"]},{"url":"https://github.com/matrix-org/matrix-android-sdk2/commit/77df720a238d17308deab83ecaa37f7a4740a17e","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web"]},{"url":"https://github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.5.1","tags":["x_refsource_MISC","x_transferred","Release Notes","Third Party Advisory","web"]},{"url":"https://github.com/matrix-org/matrix-android-sdk2/security/advisories/GHSA-fpgf-pjjv-2qgm","tags":["x_refsource_CONFIRM","x_transferred","Patch","Third Party Advisory","advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2022-39248","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-fpgf-pjjv-2qgm"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/39xxx/CVE-2022-39248.json","tags":["advisory"]},{"url":"https://github.com/matrix-org/matrix-android-sdk2","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2022-39248","title":"matrix-android-sdk2 vulnerable to Olm/Megolm protocol confusion","description":"matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, 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. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-android-sdk2 version 1.5.1 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption. 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.","status":"published","published":"2022-09-28T20:05:12Z","modified":"2025-04-23T16:54:40.093Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N","level":"high","assessor":"cna"}],"cwes":["CWE-322","CWE-287"],"updated_at":"2026-11-02T14:34:39.559326Z"}],"euvd":[{"id":"EUVD-2022-6804","description":"matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, 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. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-android-sdk2 version 1.5.1 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption. 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.","status":"published","published":"2022-09-28T20:05:12Z","modified":"2025-04-23T16:54:40Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T20:52:11.440801Z"}],"ghsa":[{"id":"GHSA-fpgf-pjjv-2qgm","title":"matrix-android-sdk2 vulnerable to Olm/Megolm protocol confusion","description":"### Impact\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. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device.\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-android-sdk2 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption.\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\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 using verify with passphrase.\n\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","status":"published","published":"2022-09-30T04:37:39Z","modified":"2023-01-29T05:05:16Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N","level":"high"}],"cwes":["CWE-287","CWE-322"],"updated_at":"2026-11-02T14:36:25.835323Z"}],"nvd":[{"id":"CVE-2022-39248","description":"matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, 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. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-android-sdk2 version 1.5.1 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption. 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.","status":"published","published":"2022-09-28T20:15:15.667Z","modified":"2026-06-17T04:57:59.573Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N","level":"high","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"primary"}],"cwes":["CWE-287","CWE-322"],"updated_at":"2026-11-02T14:07:29.026521Z"}],"osv":[{"id":"CVE-2022-39248","title":"matrix-android-sdk2 vulnerable to Olm/Megolm protocol confusion","description":"matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, 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. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-android-sdk2 version 1.5.1 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption. 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.","status":"published","published":"2022-09-28T20:05:12Z","modified":"2026-10-28T02:30:28.581014155Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N","level":"high"}],"cwes":["CWE-287","CWE-322"],"updated_at":"2026-11-02T15:44:26.53798Z"},{"id":"GHSA-fpgf-pjjv-2qgm","title":"matrix-android-sdk2 vulnerable to Olm/Megolm protocol confusion","description":"### Impact\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. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device.\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-android-sdk2 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption.\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\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 using verify with passphrase.\n\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","status":"published","published":"2022-09-30T04:37:39Z","modified":"2023-11-08T04:10:16.510187Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N","level":"high"}],"cwes":["CWE-287","CWE-322"],"updated_at":"2026-11-02T15:46:46.760785Z"}]}}