CVE-2022-39251Network attack vector

Trusted-sender impersonation via Olm/Megolm protocol confusion

Published Sep 28, 2022 · Updated Apr 23, 2025

Protocol confusion in matrix-js-sdk before 19.7.0 allows remote attackers to impersonate trusted senders through crafted to-device messages. The to-device decryption path accepts Megolm-encrypted messages where Olm is required and derives their origin from homeserver-controlled fields instead of the authenticating Olm session. Exploitation requires an attacker cooperating with a malicious homeserver and enables forged messages or malicious key-backup injection.

CVSS severity8.6
High
EPSS probability0.98%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Protocol confusion in matrix-js-sdk before 19.7.0 allows remote attackers to impersonate trusted senders through crafted to-device messages. The to-device decryption path accepts Megolm-encrypted messages where Olm is required and derives their origin from homeserver-controlled fields instead of the authenticating Olm session. Exploitation requires an attacker cooperating with a malicious homeserver and enables forged messages or malicious key-backup injection.

The record

CVE
CVE-2022-39251
Published
Sep 28, 2022
Updated
Apr 23, 2025
Vendor
The Matrix.org Foundation
Product
matrix-js-sdk
Classifications
CWE-287, CWE-322, T1565.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 28, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 19.7.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Matrix.org Foundation · matrix-js-sdkversion=< 19.7.0

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
8.6GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
CWE-322Key Exchange without Entity Authentication
T1565.002Transmitted Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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