CVE-2022-39249: Matrix Javascript SDK vulnerable to impersonation via forwarded Megolm sessions
First published: Wed Sep 28 2022(Updated: )
Matrix Javascript SDK is the Matrix Client-Server SDK for JavaScript. Prior to version 19.7.0, an attacker cooperating with a malicious homeserver can construct messages appearing to have come from another person. Such messages will be marked with a grey shield on some platforms, but this may be missing in others. This attack is possible due to the matrix-js-sdk implementing a too permissive key forwarding strategy on the receiving end. Starting with version 19.7.0, the default policy for accepting key forwards has been made more strict in the matrix-js-sdk. matrix-js-sdk will now only accept forwarded keys in response to previously issued requests and only from own, verified devices. The SDK now sets a `trusted` flag on the decrypted message upon decryption, based on whether the key used to decrypt the message was received from a trusted source. Clients need to ensure that messages decrypted with a key with `trusted = false` are decorated appropriately, for example, by showing a warning for such messages. This attack requires coordination between a malicious homeserver and an attacker, and those who trust your homeservers do not need a 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://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-6263-x97c-c4gg
- https://github.com/matrix-org/matrix-spec-proposals/pull/3061
- 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
- https://bugzilla.mozilla.org/show_bug.cgi?id=1791765
- https://www.mozilla.org/en-US/security/advisories/mfsa2022-43/
Peer vulnerabilities
(Found alongside the following vulnerabilities)
Frequently Asked Questions
What is CVE-2022-39249?
CVE-2022-39249 is a vulnerability in Thunderbird that allows a malicious server administrator to impersonate another user on the Matrix chat protocol.
How does CVE-2022-39249 affect Thunderbird users?
CVE-2022-39249 affects Thunderbird users who use the Matrix chat protocol, as they are vulnerable to an impersonation attack.
What is the severity of CVE-2022-39249?
CVE-2022-39249 has a severity level of high.
How can a malicious server administrator exploit CVE-2022-39249?
A malicious server administrator can exploit CVE-2022-39249 by faking encrypted messages to appear as if they were sent from another user on the server.
How can Thunderbird users protect themselves from CVE-2022-39249?
To protect themselves from CVE-2022-39249, Thunderbird users should update to version 102.3.1 or later.
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