CVE-2022-39248: matrix-android-sdk2 vulnerable to Olm/Megolm protocol confusion
First published: Wed Sep 28 2022(Updated: )
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 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. matrix-android-sdk2 would then additionally sign such a key backup with its device key, spilling trust over to other devices trusting the matrix-android-sdk2 device. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-android-sdk2 version 1.5.1 has been modified to only accept Olm-encrypted to-device messages and to stop signing backups on a successful decryption. 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.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Matrix Software Development Kit | <1.5.1 |
Remedy
https://github.com/matrix-org/matrix-android-sdk2/commit/77df720a238d17308deab83ecaa37f7a4740a17e
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Reference Links
- https://github.com/matrix-org/matrix-android-sdk2/commit/77df720a238d17308deab83ecaa37f7a4740a17e
- https://github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.5.1
- https://github.com/matrix-org/matrix-android-sdk2/security/advisories/GHSA-fpgf-pjjv-2qgm
- https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients
Frequently Asked Questions
What is CVE-2022-39248?
CVE-2022-39248 is a vulnerability in the matrix-android-sdk2 library for Android, allowing an attacker to construct messages that appear to be from another person without any indication.
How does CVE-2022-39248 impact Matrix SDK for Android?
CVE-2022-39248 allows an attacker cooperating with a malicious homeserver to send messages that appear to come from another person, without any indication of tampering.
What is the severity of CVE-2022-39248?
CVE-2022-39248 has a severity keyword of 'high' and a severity value of 7.5.
How can CVE-2022-39248 be fixed?
To fix CVE-2022-39248, it is recommended to upgrade to version 1.5.1 or later of the matrix-android-sdk2 library for Android.
Are there any references for CVE-2022-39248?
Yes, you can find references for CVE-2022-39248 at the following links: [Reference 1](https://github.com/matrix-org/matrix-android-sdk2/commit/77df720a238d17308deab83ecaa37f7a4740a17e), [Reference 2](https://github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.5.1), [Reference 3](https://github.com/matrix-org/matrix-android-sdk2/security/advisories/GHSA-fpgf-pjjv-2qgm).
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