CVE-2022-39248 – org.matrix.android:matrix-android-sdk2

Package

Manager: maven
Name: org.matrix.android:matrix-android-sdk2
Vulnerable Version: >=0 <1.5.1

Severity

Level: High

CVSS v3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

EPSS: 0.00208 pctl0.43264

Details

matrix-android-sdk2 vulnerable to Olm/Megolm protocol confusion ### Impact 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. ### Patches matrix-android-sdk2 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: - Cleartext `m.room_key`, `m.forwarded_room_key` and `m.secret.send` to_device messages are discarded. - Secrets received from untrusted devices are discarded. - Key backups are only usable if they have a valid signature from a trusted device (no more local trust, or trust-on-decrypt). - 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. ### Workarounds As 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. We 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. As 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. ### References Blog post: https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients ### For more information If you have any questions or comments about this advisory, e-mail us at [security@matrix.org](mailto:security@matrix.org).

Metadata

Created: 2022-09-30T04:37:39Z
Modified: 2022-09-30T04:37:39Z
Source: https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2022/09/GHSA-fpgf-pjjv-2qgm/GHSA-fpgf-pjjv-2qgm.json
CWE IDs: ["CWE-287", "CWE-322"]
Alternative ID: GHSA-fpgf-pjjv-2qgm
Finding: F006
Auto approve: 1