# CVE-2022-39251

## Summary

- **CVE ID:** CVE-2022-39251
- **Severity:** HIGH
- **CVSS Score:** 8.6 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N)
- **CWE:** CWE-322, CWE-287
- **Published:** Sep 28, 2022
- **Last Modified:** Mar 13, 2026

## 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 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. Starting with version 19.7.0, 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. This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround.

## Affected Products

- matrix-org — matrix-js-sdk (< 19.7.0)

## References

- [CNA](https://github.com/matrix-org/matrix-js-sdk/commit/a587d7c36026fe1fcf93dfff63588abee359be76)
- [CNA](https://github.com/matrix-org/matrix-js-sdk/releases/tag/v19.7.0)
- [CNA](https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients)
- [CNA](https://github.com/matrix-org/matrix-js-sdk/security/advisories/GHSA-r48r-j8fx-mq2c)
- [CNA](https://security.gentoo.org/glsa/202210-35)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.36%
- **EPSS Percentile:** 58.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-17._