Vulnerability-Lookup

CVE-2026-46482 (GCVE-0-2026-46482)

Vulnerability from cvelistv5 – Published: 2026-08-18 15:44 – Updated: 2026-08-18 17:46

Title

MyBB: Security Question insufficient validation

Summary

### 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. ### Patches MyBB 1.8.(...) resolves this issue with the following changes: - Commit: https://github.com/mybb/mybb/commit/ - `.patch`: https://github.com/mybb/mybb/commit/.patch ### 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).

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-18 17:44 UTC

CWE

CWE-636 - Not Failing Securely ('Failing Open')

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/mybb/mybb/security/advisories/…	x_refsource_CONFIRM
https://github.com/mybb/mybb/commit/bd2a3447939d3…	x_refsource_MISC
https://github.com/mybb/mybb/releases/tag/mybb_1840	x_refsource_MISC
https://mybb.com/versions/1.8.40	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
mybb	mybb	Affected: < 1.8.40	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-46482",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-18T17:44:40.432629Z",
                "version": "2.0.3"
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              "type": "ssvc"
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        "providerMetadata": {
          "dateUpdated": "2026-08-18T17:46:31.511Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
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        {
          "product": "mybb",
          "vendor": "mybb",
          "versions": [
            {
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              "version": "\u003c 1.8.40"
            }
          ]
        }
      ],
      "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` \u2014 expected to match the question session identifier (`mybb_questionsessions.sid`) \u2014 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)."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-636",
              "description": "CWE-636: Not Failing Securely (\u0027Failing Open\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-18T15:44:59.644Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
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          "name": "https://github.com/mybb/mybb/security/advisories/GHSA-v2h7-4jp7-j6hh",
          "tags": [
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          ],
          "url": "https://github.com/mybb/mybb/security/advisories/GHSA-v2h7-4jp7-j6hh"
        },
        {
          "name": "https://github.com/mybb/mybb/commit/bd2a3447939d3084a5926dd66ece04649e0e0d60",
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          "url": "https://github.com/mybb/mybb/commit/bd2a3447939d3084a5926dd66ece04649e0e0d60"
        },
        {
          "name": "https://github.com/mybb/mybb/releases/tag/mybb_1840",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mybb/mybb/releases/tag/mybb_1840"
        },
        {
          "name": "https://mybb.com/versions/1.8.40",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://mybb.com/versions/1.8.40"
        }
      ],
      "source": {
        "advisory": "GHSA-v2h7-4jp7-j6hh",
        "discovery": "UNKNOWN"
      },
      "title": "MyBB: Security Question insufficient validation"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-46482",
    "datePublished": "2026-08-18T15:44:59.644Z",
    "dateReserved": "2026-05-14T18:06:06.810Z",
    "dateUpdated": "2026-08-18T17:46:31.511Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-46482",
      "date": "2026-08-24",
      "epss": "0.00328",
      "percentile": "0.25143"
    },
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    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-46482\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-08-18T17:44:40.432629Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-08-18T17:44:41.496Z\"}}], \"cna\": {\"title\": \"MyBB: Security Question insufficient validation\", \"source\": {\"advisory\": \"GHSA-v2h7-4jp7-j6hh\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"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\"}}], \"affected\": [{\"vendor\": \"mybb\", \"product\": \"mybb\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003c 1.8.40\"}]}], \"references\": [{\"url\": \"https://github.com/mybb/mybb/security/advisories/GHSA-v2h7-4jp7-j6hh\", \"name\": \"https://github.com/mybb/mybb/security/advisories/GHSA-v2h7-4jp7-j6hh\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"https://github.com/mybb/mybb/commit/bd2a3447939d3084a5926dd66ece04649e0e0d60\", \"name\": \"https://github.com/mybb/mybb/commit/bd2a3447939d3084a5926dd66ece04649e0e0d60\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/mybb/mybb/releases/tag/mybb_1840\", \"name\": \"https://github.com/mybb/mybb/releases/tag/mybb_1840\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://mybb.com/versions/1.8.40\", \"name\": \"https://mybb.com/versions/1.8.40\", \"tags\": [\"x_refsource_MISC\"]}], \"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` \\u2014 expected to match the question session identifier (`mybb_questionsessions.sid`) \\u2014 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).\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-636\", \"description\": \"CWE-636: Not Failing Securely (\u0027Failing Open\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-08-18T15:44:59.644Z\"}}}",
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}

FKIE_CVE-2026-46482

Vulnerability from fkie_nvd - Published: 2026-08-18 16:17 - Updated: 2026-08-18 18:17

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/mybb/mybb/commit/bd2a3447939d3084a5926dd66ece04649e0e0d60
	security-advisories@github.com	https://github.com/mybb/mybb/releases/tag/mybb_1840
	security-advisories@github.com	https://github.com/mybb/mybb/security/advisories/GHSA-v2h7-4jp7-j6hh
	security-advisories@github.com	https://mybb.com/versions/1.8.40

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "mybb",
          "vendor": "mybb",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.8.40"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "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` \u2014 expected to match the question session identifier (`mybb_questionsessions.sid`) \u2014 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)."
    }
  ],
  "id": "CVE-2026-46482",
  "lastModified": "2026-08-18T18:17:38.290",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-46482",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-18T17:44:40.432629Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-18T16:17:09.350",
  "references": [
    {
      "source": "security-advisories@github.com",
      "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"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-636"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-46482 (GCVE-0-2026-46482)

FKIE_CVE-2026-46482

Tags

Sightings

Nomenclature