CVE-2022-39251 | Matrix Javascript SDK vulnerable to Olm/Megolm protocol confusion

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.

Published: 2022-09-28 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2022-39251 is rated Moderate Risk (52.3/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.28%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2022-39251

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-28 0.37% 0.28% -0.09%
2 2025-12-08 0.18% 0.37% +0.19%
3 2025-11-21 — 0.18% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2022-39251

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.6 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 4.0 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2022-39251

GitHub Security Advisory for CVE-2022-39251

GHSA-r48r-j8fx-mq2c · Severity: high · Ecosystem: npm — matrix-js-sdk subject to user spoofing via Olm/Megolm protocol confusion

OS Trackers for CVE-2022-39251

vendor priority summary link
alpine high CVE-2022-39251: 2 source package rows (element-web, riot-web); 8 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 8, open 0. https://security.alpinelinux.org/vuln/CVE-2022-39251
debian not yet assigned CVE-2022-39251 not yet assigned priority: Debian including 1 source packages (node-matrix-js-sdk), 1 status rows across 1 suites (bullseye): open 1. https://security-tracker.debian.org/tracker/CVE-2022-39251
gentoo high CVE-2022-39251: 1 GLSA(s) (202210-35), 2 atom(s) (mail-client/thunderbird, mail-client/thunderbird-bin); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2022-39251
redhat high — https://access.redhat.com/security/cve/CVE-2022-39251
suse high CVE-2022-39251 severity important: SUSE including 11 source package names (MozillaThunderbird-102.3.1-1.1, MozillaThunderbird-102.4.0-150200.8.85.1, …), 50 product×package rows across 19 product lines (SUSE Liberty Linux 7, SUSE Liberty Linux 8, … (19 product lines)): Fixed 50. https://www.suse.com/security/cve/CVE-2022-39251/
ubuntu medium CVE-2022-39251 medium priority: Ubuntu including 2 source packages (node-matrix-js-sdk, thunderbird), 26 status rows across 13 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): ignored 7, not-affected 6, needs-triage 5, DNE 4, released 4. https://ubuntu.com/security/CVE-2022-39251

Affected software / configurations for CVE-2022-39251

Vendor Product Version Raw CPE
matrix javascript_sdk < 19.7.0 cpe:2.3:a:matrix:javascript_sdk:*:*:*:*:*:node.js:*:*

References for CVE-2022-39251

cvelogic Threat Intelligence