{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "4.1.0"
              },
              {
                "fixed": "5.3.50"
              },
              {
                "introduced": "5.4.0-RC1"
              },
              {
                "fixed": "5.7.12"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "a112b68dcb5215b01f2c4c4b8de6bcb3d3b9ae81"
            },
            {
              "introduced": "c5e3841e5107ab36ae2bf7795fb8d51d3d30f88b"
            },
            {
              "fixed": "a11109b60dedcbd99e32a4e8550afdadb500f2c5"
            },
            {
              "fixed": "a6543f49a92187a7368f51b290179c4795386e23"
            },
            {
              "fixed": "2ea6117f9049db7221679251cfc41e67d941a74b"
            }
          ],
          "repo": "https://github.com/contao/contao",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-mfxh-vp55-7gc6"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-204",
      "CWE-770"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107843.json"
  },
  "details": "Contao is an Open Source CMS. From version 4.1.0 until 5.3.50 and 5.7.12, ModuleRegistration::compile() enters its follow-up registration branch on any POST to a page containing the registration module without verifying FORM_SUBMIT or the preceding captcha result. resendActivationMail() can then invoke OptInToken::send() without rate limiting, allowing an unauthenticated attacker to cause repeated activation emails to be sent to an address with a pending registration and to determine whether that pending registration exists. The branch is reachable only when reg_activate is enabled and the target has an unconfirmed registration and opt-in token. This issue is fixed in versions 5.3.50 and 5.7.12.",
  "id": "CVE-2026-107843",
  "modified": "2026-10-15T02:30:28.474985447Z",
  "published": "2026-10-09T19:21:32.011Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/contao/contao/releases/tag/5.3.50"
    },
    {
      "type": "WEB",
      "url": "https://github.com/contao/contao/releases/tag/5.7.12"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/107xxx/CVE-2026-107843.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/contao/contao/security/advisories/GHSA-mfxh-vp55-7gc6"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-107843"
    },
    {
      "type": "FIX",
      "url": "https://github.com/contao/contao/commit/2ea6117f9049db7221679251cfc41e67d941a74b"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Contao: The registration module re-sends activation mails on any unauthenticated POST, with no throttle and no captcha check"
}