{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4442142c7111cf051d30d9015de7266a515bfc95"
            }
          ],
          "repo": "https://github.com/matrix-org/matrix-ios-sdk",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-qxr3-5jmq-xcf4"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-287",
      "CWE-322"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/39xxx/CVE-2022-39257.json"
  },
  "details": "Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, 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 matrix-ios-sdk implementing a too permissive key forwarding strategy. The default policy for accepting key forwards has been made more strict in the matrix-ios-sdk version 0.23.19. matrix-ios-sdk 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). This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround.",
  "id": "CVE-2022-39257",
  "modified": "2026-04-01T23:08:56.519513629Z",
  "published": "2022-09-28T20:55:10Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/matrix-org/matrix-ios-sdk/releases/tag/v0.23.19"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/39xxx/CVE-2022-39257.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/matrix-org/matrix-ios-sdk/security/advisories/GHSA-qxr3-5jmq-xcf4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-39257"
    },
    {
      "type": "FIX",
      "url": "https://github.com/matrix-org/matrix-ios-sdk/commit/5ca86c328a5faaab429c240551cb9ca8f0f6262c"
    },
    {
      "type": "ARTICLE",
      "url": "https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Matrix iOS SDK vulnerable to impersonation via forwarded Megolm sessions"
}