phpMyFAQ Two-Factor Authentication Bypass via Brute Force

Executive Summary

This vulnerability affects phpMyFAQ versions 4.1.0 to 4.2.0-beta. It involves the removeTwofactorConfig() endpoint lacking brute-force lockout protection, allowing attackers with a valid session and CSRF token to repeatedly guess TOTP codes and permanently disable 2FA for an account.

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Detection Guidance

Monitor logs for repeated POST requests to /api/user/remove-twofactor with invalid TOTP codes. Check for unusual account activity where 2FA is disabled without user action. Use network traffic analysis to detect brute-force attempts targeting this endpoint.

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Impact Analysis

If exploited, this vulnerability allows an attacker to bypass 2FA protections, potentially gaining persistent access to an account even after the initial session compromise. This could lead to unauthorized data access or modifications.

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Compliance Impact

This vulnerability could violate compliance requirements that mandate strong authentication controls, such as GDPR's security principle or HIPAA's access controls. Disabling 2FA may lead to unauthorized data exposure or breaches.

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Mitigation Strategies

Apply the latest phpMyFAQ patch to versions 4.2.0-beta or later. Implement rate limiting on the /api/user/remove-twofactor endpoint. Review logs for suspicious activity and disable affected accounts if exploitation is detected.

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