{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "source": "REFERENCES"
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5046c56b515d4593297a4f65b0c6ccb0b55baa01"
            },
            {
              "fixed": "e9942c6d19ac1709b3df7357cfb8810774c8d3ac"
            }
          ],
          "repo": "https://github.com/mybb/mybb",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-f626-53q9-pqm9"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-93"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45125.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "fixed": "1.8.40"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "MyBB is free and open source forum software. Prior to 1.8.40, the Email User controller does not sanitize sender names correctly, resulting in mail header injection. member.php?action=do_emailuser accepts the fromname HTTP parameter for guests or the stored username for authenticated users when the cansendemail group permission is enabled. When mail_handler is set to the default PHP mail value, the sender name is used without sanitization in Return-Path and Reply-To headers, allowing arbitrary headers to be injected with CRLF sequences. This issue is fixed in version 1.8.40.",
  "id": "CVE-2026-45125",
  "modified": "2026-08-20T03:30:21.858848628Z",
  "published": "2026-08-18T15:50:38.936Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mybb/mybb/releases/tag/mybb_1840"
    },
    {
      "type": "WEB",
      "url": "https://mybb.com/versions/1.8.40"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45125.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/mybb/mybb/security/advisories/GHSA-f626-53q9-pqm9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45125"
    },
    {
      "type": "FIX",
      "url": "https://github.com/mybb/mybb/commit/5046c56b515d4593297a4f65b0c6ccb0b55baa01"
    }
  ],
  "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": "MyBB: Email User CRLF injection"
}