CVE-2022-39250 Matrix JavaScript SDK vulnerable to key/device identifier confusion in SAS verification

High 8.6 Published 29 Sep 2022 Updated 23 Apr 2025

An attacker with a malicious homeserver can bypass SAS verification to inject their own identity, causing devices to trust the attacker instead of the intended user.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2022-39250?

CVE-2022-39250 is a high-severity authentication bypass vulnerability in matrix-org matrix-js-sdk, published on 29 Sep 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Matrix JavaScript SDK is the Matrix Client-Server software development kit (SDK) for JavaScript. Prior to version 19.7.0, an attacker cooperating with a malicious homeserver could interfere with the verification flow between two users, injecting its own cross-signing user identity in place of one of the users’ identities. This would lead to the other device trusting/verifying the user identity under the control of the homeserver instead of the intended one. The vulnerability is a bug in the matrix-js-sdk, caused by checking and signing user identities and devices in two separate steps, and inadequately fixing the keys to be signed between those steps. Even though the attack is partly made possible due to the design decision of treating cross-signing user identities as Matrix devices on the server side (with their device ID set to the public part of the user identity key), no other examined implementations were vulnerable. Starting with version 19.7.0, the matrix-js-sdk has been modified to double check that the key signed is the one that was verified instead of just referencing the key by ID. An additional check has been made to report an error when one of the device ID matches a cross-signing key. As this attack requires coordination between a malicious homeserver and an attacker, those who trust their homeservers do not need a particular workaround.

Weakness: CWE-322, CWE-287

Which versions are affected by CVE-2022-39250?

2 open source packages ship an affected version, including matrix-js-sdk. It affects 1 product.

Package	Affected	Fixed in
`matrix-js-sdk` npm	All versions	`19.7.0`
`matrix-js-sdk` npm	All versions	`19.7.0`

Products include Matrix Javascript Sdk.

How do I fix CVE-2022-39250?

Upgrade matrix-js-sdk to 19.7.0 or later.

Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.

Is CVE-2022-39250 being exploited?

There is no known exploitation of CVE-2022-39250 in the wild and no public exploit code.

Sources

Also known as CLEANSTART-2024-YV48715, DEBIAN-CVE-2022-39250, GHSA-5w8r-8pgj-5jmf, UBUNTU-CVE-2022-39250.