CVE-2026-46482

MyBB: Security Question insufficient validation

5.3 Medium

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

Details

The public Registration workflow (member.php?action=do_register) 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 to report possible security concerns or to learn more about security research at MyBB.

Contact

The security team can be reached at [email protected].

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: Low
Availability: None

Exploit likelihood

0.45%Up 0.4 points since Jun 12, 2026

What each source reports

CVE List Score used 5.3

MyBB: 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

Details

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 to report possible security concerns or to learn more about security research at MyBB.

Contact

The security team can be reached at [email protected].

Record: CVE-2026-46482
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness: CWE-636
Updated: 2026-11-02

EUVDEUVD-2026-61052 5.3

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

Details

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 to report possible security concerns or to learn more about security research at MyBB.

Contact

The security team can be reached at [email protected].

Record: EUVD-2026-61052
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Updated: 2026-11-02

NVD 5.3

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

Details

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 to report possible security concerns or to learn more about security research at MyBB.

Contact

The security team can be reached at [email protected].

Record: CVE-2026-46482
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness: CWE-636
Updated: 2026-11-02

OSV 5.3

MyBB: 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

Details

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 to report possible security concerns or to learn more about security research at MyBB.

Contact

The security team can be reached at [email protected].

Record: CVE-2026-46482
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Weakness: CWE-636
Updated: 2026-11-02

Affected products

mybb

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-46482 is a medium vulnerability (CVSS 5.3) in Mybb, published August 18, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.45%, the 39th percentile. No source names a fixed version.