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).
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| mybb | mybb | affected |
|
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No data available yet.
No remediation available yet.
Tracking
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Tue, 18 Aug 2026 16:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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 [security@mybb.com](mailto:security@mybb.com). | |
| Title | MyBB: Security Question insufficient validation | |
| Weaknesses | CWE-636 | |
| References |
| |
| Metrics |
cvssV3_1
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Subscriptions
No data.
MITRE
Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-08-18T17:46:31.511Z
Reserved: 2026-05-14T18:06:06.810Z
Link: CVE-2026-46482
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-08-18T16:17:09.350
Modified: 2026-08-18T16:17:09.350
Link: CVE-2026-46482
Redhat
No data.
OpenCVE Enrichment
No data.
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CWE-636
Not Failing Securely ('Failing Open')