CVE-2022-39249

Matrix Javascript SDK vulnerable to impersonation via forwarded Megolm sessions

Published Sep 28, 2022 CVSS 3.1 · 7.5 High EPSS 1.3% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2022-6714 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.
Github GHSA Github GHSA GHSA-6263-x97c-c4gg matrix-js-sdk subject to impersonated messages due to permissive key forwarding
Ubuntu USN Ubuntu USN USN-5724-1 Thunderbird vulnerabilities
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Apr 23, 2025, 4:55 PM
Reserved
Sep 2, 2022, 12:00 AM
Status
Modified
Published
Sep 28, 2022, 8:15 PM
Modified
Jun 17, 2026, 4:57 AM
Severity
Important
Public date
Sep 28, 2022, 12:00 AM