CVE-2022-39246 matrix-android-sdk2 vulnerable to impersonation via forwarded Megolm sessions

2022-09-2820:00:19

CWE-322

CWE-287

GitHub_M

www.cve.org

cve-2022-39246

megolm sessions

impersonation

key forwarding

malicious homeserver

7.5 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

HIGH

Availability Impact

NONE

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

0.001 Low

EPSS

Percentile

42.3%

JSON

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).

CNA Affected

[
  {
    "product": "matrix-android-sdk2",
    "vendor": "matrix-org",
    "versions": [
      {
        "status": "affected",
        "version": "< 1.5.1"
      }
    ]
  }
]