{"id":"CVE-2026-46482","state":"PUBLISHED","title":"MyBB: Security Question insufficient validation","description":"### 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).","publishedAt":"2026-08-18T15:44:59.644Z","updatedAt":"2026-08-18T17:46:31.511Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["mybb mybb"],"affected":[{"vendor":"mybb","product":"mybb","versions":[{"version":"< 1.8.40","status":"affected"}]}],"references":["https://github.com/mybb/mybb/security/advisories/GHSA-v2h7-4jp7-j6hh","https://github.com/mybb/mybb/commit/bd2a3447939d3084a5926dd66ece04649e0e0d60","https://github.com/mybb/mybb/releases/tag/mybb_1840","https://mybb.com/versions/1.8.40"],"weaknesses":["CWE-636"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/46xxx/CVE-2026-46482.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-46482","state":"PUBLISHED","datePublished":"2026-08-18T15:44:59.644Z","dateUpdated":"2026-08-18T17:46:31.511Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-05-14T18:06:06.810Z"},"containers":{"cna":{"title":"MyBB: Security Question insufficient validation","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)."}],"affected":[{"vendor":"mybb","product":"mybb","versions":[{"version":"< 1.8.40","status":"affected"}]}],"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"]}],"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","lang":"en","description":"CWE-636: Not Failing Securely ('Failing Open')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-18T15:44:59.644Z"},"source":{"advisory":"GHSA-v2h7-4jp7-j6hh","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-18T17:44:40.432629Z","id":"CVE-2026-46482","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-18T17:46:31.511Z"}}]}}}