CVE-2026-46482MyBB: Security Question insufficient validation

### 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).

CVSS

5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Weakness (CWE)

CWE-636

Known exploited

Not in CISA's KEV catalog

EPSS (exploitation in the next 30 days)

Not loaded for this CVE

Assigned by

GitHub_M

NVD analysis

Deferred

Record last updated

Aug 18, 2026

First seen by InfoSec Signals

Oct 9, 2026

The CVE record on cve.org · NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.