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.
Published 2022-09-28 20:15:16
Updated 2022-09-30 16:24:10
Source GitHub, Inc.
View at NVD,   CVE.org
Vulnerability category: BypassGain privilege

Exploit prediction scoring system (EPSS) score for CVE-2022-39248

0.09%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 37 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2022-39248

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
7.5
HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
3.9
3.6
NIST
8.6
HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
3.9
4.0
GitHub, Inc.

CWE ids for CVE-2022-39248

  • When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
    Assigned by: security-advisories@github.com (Primary)
  • The product performs a key exchange with an actor without verifying the identity of that actor.
    Assigned by: security-advisories@github.com (Primary)

References for CVE-2022-39248

Products affected by CVE-2022-39248

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