CVE-2026-46482 MyBB: Security Question insufficient validation
Attackers can bypass the registration security question CAPTCHA by providing invalid identifiers, allowing automated account creation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-46482?
CVE-2026-46482 is a medium-severity vulnerability in mybb, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
### 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 [[email protected]](mailto:[email protected]).
Weakness: CWE-636
Which versions are affected by CVE-2026-46482?
How do I fix CVE-2026-46482?
No fix has been published for CVE-2026-46482 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-46482 being exploited?
There is no known exploitation of CVE-2026-46482 in the wild and no public exploit code.
Sources
Also known as GHSA-v2h7-4jp7-j6hh.