CVE-2022-39246: matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, an attacker cooperating with a malicious homeserver can construct messages ...

Description

matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, 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 key forwarding strategy implemented in the matrix-android-sdk2 that is too permissive. Starting with version 1.5.1, the default policy for accepting key forwards has been made more strict in the matrix-android-sdk2. The matrix-android-sdk2 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). As a workaroubnd, current users of the SDK can disable key forwarding in their forks using `CryptoService#enableKeyGossiping(enable: Boolean)`.

Metrics

CVSS 3.1

5.3/10

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

EPSS Probability

0.63%

45.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Matrix	Software Development Kit	< 1.5.1

References

https://github.com/matrix-org/matrix-android-sdk2/commit/77df720a238d17308deab83ecaa37f7a4740a17ePatch, Third Party Advisory
https://github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.5.1Release Notes, Third Party Advisory
https://github.com/matrix-org/matrix-android-sdk2/security/advisories/GHSA-2pvj-p485-cp3mMitigation, Patch, Third Party Advisory
https://github.com/matrix-org/matrix-spec-proposals/pull/3061Patch, Third Party Advisory
https://github.com/matrix-org/matrix-android-sdk2/commit/77df720a238d17308deab83ecaa37f7a4740a17ePatch, Third Party Advisory
https://github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.5.1Release Notes, Third Party Advisory
https://github.com/matrix-org/matrix-android-sdk2/security/advisories/GHSA-2pvj-p485-cp3mMitigation, Patch, Third Party Advisory
https://github.com/matrix-org/matrix-spec-proposals/pull/3061Patch, Third Party Advisory

Timeline

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

Frequently Asked Questions

What is CVE-2022-39246?

matrix-android-sdk2 is the Matrix SDK for Android. Prior to version 1.5.1, 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 key forwarding strategy implemented in the matrix-android-sdk2 that is too permissive. Starting with version 1.5.1, the default policy for accepting key forwards has been made more strict in the matrix-android-sdk2. The matrix-android-sdk2 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). As a workaroubnd, current users of the SDK can disable key forwarding in their forks using `CryptoService#enableKeyGossiping(enable: Boolean)`.

How severe is CVE-2022-39246?

CVE-2022-39246 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.63% probability of exploitation in the next 30 days.

How do I fix CVE-2022-39246?

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.