GHSA-r48r-j8fx-mq2c

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Source
https://github.com/advisories/GHSA-r48r-j8fx-mq2c
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2022/09/GHSA-r48r-j8fx-mq2c/GHSA-r48r-j8fx-mq2c.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-r48r-j8fx-mq2c
Aliases
Published
2022-09-30T00:41:24Z
Modified
2023-11-01T04:59:47.586508Z
Severity
  • 8.6 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N CVSS Calculator
Summary
matrix-js-sdk subject to user spoofing via Olm/Megolm protocol confusion
Details

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.

These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm.

Patches

matrix-js-sdk has been modified to only accept Olm-encrypted to-device messages.

Out of caution, several other checks have been audited or added: - Cleartext m.room_key, m.forwarded_room_key and m.secret.send todevice 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 senderkey, 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 verifying with your security passphrase instead.

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.

References

Affected packages

npm / matrix-js-sdk

Package

Affected ranges

Type
SEMVER
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
19.7.0