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CVE-2026-46482

Estado: AplazadaMedia (5.3)—

### Impact The registration component does not validate the text-based _Security Question_ CAPTCHA correctly, allowing attackers to bypass the challenge via a specially crafted value.

[CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N)

### Details The public _Registration_ workflow ([`member.php?action=do_register`](https://github.com/mybb/mybb/blob/mybb_1839/member.php#L262-L307)) accepts a hidden field `question_id` — expected to match the question session identifier (`mybb_questionsessions.sid`) — and validates the challenge answer without a fail-closed fallback for invalid identifiers. If the value is blank, forged, or expired, the request continues without a question-related error.

Leer descripción completaMostrar menos

### Patches MyBB 1.8.(...) resolves this issue with the following changes:

### References - Release Notes: https://mybb.com/versions/1.8.(...)/

### For more information Go to [mybb.com/security](https://mybb.com/security/) to report possible security concerns or to learn more about security research at MyBB.

### Contact The security team can be reached at [security@mybb.com](mailto:security@mybb.com).

Detalles técnicos trazas, registros y código del informe original
- Commit: https://github.com/mybb/mybb/commit/
  - `.patch`: https://github.com/mybb/mybb/commit/.patch

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Mybb — MybbAI

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2026-46482",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-46482",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-08-18T17:44:40.432629Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "mybb",
          "product": "mybb",
          "versions": [
            {
              "status": "affected",
              "version": "< 1.8.40"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-08-18T16:17:09.350",
  "references": [
    {
      "url": "https://github.com/mybb/mybb/commit/bd2a3447939d3084a5926dd66ece04649e0e0d60",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/mybb/mybb/releases/tag/mybb_1840",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/mybb/mybb/security/advisories/GHSA-v2h7-4jp7-j6hh",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://mybb.com/versions/1.8.40",
      "source": "security-advisories@github.com"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-636"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "### Impact\nThe registration component does not validate the text-based _Security Question_ CAPTCHA correctly, allowing attackers to bypass the challenge via a specially crafted value.\n\n\n[CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N](https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N)\n\n### Details\nThe public _Registration_ workflow ([`member.php?action=do_register`](https://github.com/mybb/mybb/blob/mybb_1839/member.php#L262-L307)) accepts a hidden field `question_id` — expected to match the question session identifier (`mybb_questionsessions.sid`) — and validates the challenge answer without a fail-closed fallback for invalid identifiers. If the value is blank, forged, or expired, the request continues without a question-related error.\n\n### Patches\nMyBB 1.8.(...) resolves this issue with the following changes:\n\n- Commit: https://github.com/mybb/mybb/commit/\n  - `.patch`: https://github.com/mybb/mybb/commit/.patch\n\n### References\n- Release Notes: https://mybb.com/versions/1.8.(...)/\n\n### For more information\nGo to [mybb.com/security](https://mybb.com/security/) to report possible security concerns or to learn more about security research at MyBB.\n\n### Contact\nThe security team can be reached at [security@mybb.com](mailto:security@mybb.com)."
    }
  ],
  "lastModified": "2026-09-08T21:02:26.047",
  "sourceIdentifier": "security-advisories@github.com"
}