CAPTCHA Bypass Vulnerability in MyBB Registration Process
CVE-2026-46482

5.3MEDIUM

Key Information:

Vendor

Mybb

Status
Mybb
Vendor
CVE Published:
18 August 2026

What is CVE-2026-46482?

A vulnerability in the registration component of MyBB allows attackers to bypass the CAPTCHA challenge due to improper validation of the security question identifier. Specifically, the component accepts a hidden field that does not enforce strict validation checks, enabling potential unauthorized access. This issue arises from the acceptance of blank, forged, or expired identifiers without triggering an error, thus failing to protect the registration workflow.

Affected Version(s)

mybb < 1.8.40

References

https://github.com/mybb/mybb/security/advisories/GHSA-v2h...
x_refsource_CONFIRM
https://github.com/mybb/mybb/commit/bd2a3447939d3084a5926...
x_refsource_MISC
https://github.com/mybb/mybb/releases/tag/mybb_1840
x_refsource_MISC

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.