CVE-2022-39250: Matrix JavaScript SDK vulnerable to key/device identifier confusion in SAS verification
First published: Wed Sep 28 2022(Updated: )
Matrix JavaScript SDK is the Matrix Client-Server software development kit (SDK) for JavaScript. Prior to version 19.7.0, an attacker cooperating with a malicious homeserver could interfere with the verification flow between two users, injecting its own cross-signing user identity in place of one of the users’ identities. This would lead to the other device trusting/verifying the user identity under the control of the homeserver instead of the intended one. The vulnerability is a bug in the matrix-js-sdk, caused by checking and signing user identities and devices in two separate steps, and inadequately fixing the keys to be signed between those steps. Even though the attack is partly made possible due to the design decision of treating cross-signing user identities as Matrix devices on the server side (with their device ID set to the public part of the user identity key), no other examined implementations were vulnerable. Starting with version 19.7.0, the matrix-js-sdk has been modified to double check that the key signed is the one that was verified instead of just referencing the key by ID. An additional check has been made to report an error when one of the device ID matches a cross-signing key. As this attack requires coordination between a malicious homeserver and an attacker, those who trust their homeservers do not need a particular workaround.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Mozilla Thunderbird | <102.3.1 | 102.3.1 |
| Matrix Javascript Sdk | <19.7.0 |
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Reference Links
- https://bugzilla.mozilla.org/show_bug.cgi?id=1791765
- https://www.mozilla.org/en-US/security/advisories/mfsa2022-43/
- https://github.com/matrix-org/matrix-js-sdk/commit/a587d7c36026fe1fcf93dfff63588abee359be76
- https://github.com/matrix-org/matrix-js-sdk/releases/tag/v19.7.0
- https://github.com/matrix-org/matrix-js-sdk/security/advisories/GHSA-5w8r-8pgj-5jmf
- https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients
- https://security.gentoo.org/glsa/202210-35
Peer vulnerabilities
(Found alongside the following vulnerabilities)
Frequently Asked Questions
What is CVE-2022-39250?
CVE-2022-39250 is a vulnerability in the Matrix JavaScript SDK that allows an attacker cooperating with a malicious homeserver to impersonate a user in the verification flow between two users.
What is the severity of CVE-2022-39250?
CVE-2022-39250 has a high severity rating of 7.
How does CVE-2022-39250 affect Thunderbird users?
CVE-2022-39250 affects Thunderbird users who use the Matrix chat protocol.
How can an attacker exploit CVE-2022-39250?
An attacker cooperating with a malicious homeserver can exploit CVE-2022-39250 to inject their own cross-signing user identity in place of one of the users in the verification flow.
How can I mitigate CVE-2022-39250?
To mitigate CVE-2022-39250, update the Matrix JavaScript SDK to version 19.7.0 or later.
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