{"id":"CVE-2026-46482","summary":"MyBB: Security Question insufficient validation","details":"### 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).","aliases":["GHSA-v2h7-4jp7-j6hh"],"modified":"2026-08-20T03:54:21.915307829Z","published":"2026-08-18T15:44:59.644Z","database_specific":{"unresolved_ranges":[{"source":"AFFECTED_FIELD","extracted_events":[{"fixed":"1.8.40"}]}],"cna_assigner":"GitHub_M","cwe_ids":["CWE-636"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46482.json"},"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/2026/46xxx/CVE-2026-46482.json"},{"type":"ADVISORY","url":"https://github.com/mybb/mybb/security/advisories/GHSA-v2h7-4jp7-j6hh"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-46482"},{"type":"FIX","url":"https://github.com/mybb/mybb/commit/bd2a3447939d3084a5926dd66ece04649e0e0d60"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mybb/mybb","events":[{"introduced":"0"},{"fixed":"bd2a3447939d3084a5926dd66ece04649e0e0d60"},{"fixed":"e9942c6d19ac1709b3df7357cfb8810774c8d3ac"}],"database_specific":{"source":"REFERENCES"}}],"versions":["mybb_1840_build","mybb_1839","mybb_1839_build","mybb_1838","mybb_1838_build","mybb_1837","mybb_1837_build","mybb_1836","mybb_1835_build","mybb_1835","mybb_1834","mybb_1834_build","mybb_1833","mybb_1833_build","mybb_1832","mybb_1832_build","mybb_1831","mybb_1831_build","mybb_1829","mybb_1828","mybb_1828_build","mybb_1827_build","mybb_1827","mybb_1823_build","mybb_1823","mybb_1822","mybb_1822_build","mybb_1821pl1","mybb_1821","mybb_1821_build","mybb_1817_build","mybb_1817","mybb_1820","mybb_1820_build","mybb_1820-rc","mybb_1819","mybb_1818","mybb_1819_build","mybb_1818_build","mybb_1816","mybb_1816_build","mybb_1815","mybb_1815_build","mybb_1814","mybb_1813","mybb_1812","mybb_1811","mybb_1810","mybb_1809","mybb_1808","mybb_1807","mybb_1806","mybb_1805","mybb_1804","mybb_1800","mybb_1801"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-46482.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}