CVE-2022-39249: 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...

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS Probability

0.94%

56.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Matrix	Javascript Sdk	< 19.7.0

References

https://github.com/matrix-org/matrix-js-sdk/commit/a587d7c36026fe1fcf93dfff63588abee359be76Patch, Third Party Advisory
https://github.com/matrix-org/matrix-js-sdk/releases/tag/v19.7.0Release Notes, Third Party Advisory
https://github.com/matrix-org/matrix-js-sdk/security/advisories/GHSA-6263-x97c-c4ggThird Party Advisory
https://github.com/matrix-org/matrix-spec-proposals/pull/3061Patch, Third Party Advisory
https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clientsVendor Advisory
https://security.gentoo.org/glsa/202210-35Third Party Advisory
https://github.com/matrix-org/matrix-js-sdk/commit/a587d7c36026fe1fcf93dfff63588abee359be76Patch, Third Party Advisory
https://github.com/matrix-org/matrix-js-sdk/releases/tag/v19.7.0Release Notes, Third Party Advisory
https://github.com/matrix-org/matrix-js-sdk/security/advisories/GHSA-6263-x97c-c4ggThird Party Advisory
https://github.com/matrix-org/matrix-spec-proposals/pull/3061Patch, Third Party Advisory
https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clientsVendor Advisory
https://security.gentoo.org/glsa/202210-35Third Party Advisory

Timeline

Published: Sep 28, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2022-39249?

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.

How severe is CVE-2022-39249?

CVE-2022-39249 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.94% probability of exploitation in the next 30 days.

How do I fix CVE-2022-39249?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.