Vulnerability identifier: #VU56489

Vulnerability risk: Medium

CVSSv3.1: 5.2 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-40824

CWE-ID: CWE-200

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Matrix SDK for Android
Universal components / Libraries / Software for developers

Vendor: Matrix.org

Description

The vulnerability allows a remote attacker to gain access to sensitive information.

The vulnerability exists due to a logic error in the room key sharing functionality of Element Android in Matrix SDK for Android. In certain circumstances it is possible to trick vulnerable clients into disclosing encryption keys for messages previously sent by that client to user accounts later compromised by an attacker.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Matrix SDK for Android: 0.0.1 - 1.2.1

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External links
http://github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.2.2
http://matrix.org/blog/2021/09/13/vulnerability-disclosure-key-sharing

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.