{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "2.9.1"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "f9d59c2e447af42e2c3dec5a56b1bb25c7292859"
            },
            {
              "fixed": "d645d7b5b7d03218b0bc8971ef041c991a63f5f7"
            }
          ],
          "repo": "https://github.com/mikel/mail",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-mvxr-6m87-mv2q"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-436"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63435.json"
  },
  "details": "Mail is an internet library for Ruby designed to handle email generation, parsing, and sending. Prior to 2.9.1, Mail::Utilities.q_value_decode and Mail::Utilities.b_value_decode used a single String#match and an overly greedy charset capture to decode only the first RFC 2047 encoded-word and mishandle surrounding or subsequent text. A crafted malformed encoded-word in an address display name or local part could cross ? delimiters and make decoded From, To, or Reply-To header values differ from the raw values inspected by a human reviewer or downstream parser, enabling apparent sender or recipient spoofing, phishing, or authorization-check bypass. This issue is fixed in version 2.9.1.",
  "id": "CVE-2026-63435",
  "modified": "2026-09-04T03:30:48.221353042Z",
  "published": "2026-09-01T20:09:20.820Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mikel/mail/releases/tag/2.9.1"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63435.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/mikel/mail/security/advisories/GHSA-mvxr-6m87-mv2q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63435"
    },
    {
      "type": "FIX",
      "url": "https://github.com/mikel/mail/commit/f9d59c2e447af42e2c3dec5a56b1bb25c7292859"
    },
    {
      "type": "FIX",
      "url": "https://github.com/mikel/mail/pull/1664"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mail: Email address spoofing via malformed RFC 2047 encoded-words"
}