CVE-2026-56737 in phpMyFAQ
Summary
by MITRE • 09/24/2026
phpMyFAQ is an open source FAQ web application. Versions 3.2.0 through 4.1.5 contain an authentication bypass in its public two-factor authentication verification flow: an unauthenticated attacker can submit an account’s numeric user ID and a valid or brute-forced six-digit TOTP code without first authenticating with the account password, allowing takeover of any 2FA-enabled account, including administrator accounts. Version 4.1.6 is patched by binding TOTP verification to a session established after successful password authentication and limiting failed TOTP attempts. No official workaround is documented; affected installations should upgrade to 4.1.6 or later.
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Analysis
by VulDB Data Team • 09/24/2026
The vulnerability identified in phpMyFAQ versions 3.2.0 through 4.1.5 represents a critical failure in the implementation of multi-factor authentication, specifically within the public two-factor authentication verification flow. This flaw allows an unauthenticated attacker to bypass the primary password-based authentication mechanism entirely. By directly submitting a numeric user ID alongside a valid or brute-forced six-digit Time-Based One-Time Password (TOTP) code, the application erroneously grants access without requiring the initial proof of identity via password entry. This architectural oversight effectively nullifies the security benefits provided by two-factor authentication, as it reduces the attack surface to merely guessing or obtaining a user ID and cracking a short-lived numeric token, which is significantly easier than bypassing both layers sequentially.
From a technical perspective, this issue stems from an improper separation of concerns in the authentication state machine. The verification endpoint for TOTP codes does not validate that the requesting session has already passed the password-based login phase. In secure implementations, the second factor should only be processed if the first factor has been successfully verified and a temporary authenticated session or token exists. Here, the system treats the TOTP code as sufficient standalone proof of identity when paired with an identifier, ignoring the prerequisite authentication step. This design flaw enables direct account takeover for any user who has enabled two-factor authentication, including high-privilege administrator accounts that manage content and configuration settings within the FAQ application.
The operational impact of this vulnerability is severe due to its potential for remote exploitation without prior access. An attacker can automate the discovery of valid numeric user IDs through enumeration techniques or by leveraging other information disclosure vulnerabilities if present. Once a valid ID is identified, the six-digit TOTP code space is small enough (one million possibilities) that brute-force attacks are feasible within minutes using modern computing resources, especially if rate limiting is not enforced on the verification endpoint. Successful exploitation leads to complete compromise of user accounts, resulting in unauthorized access to sensitive data stored within the FAQ system, potential defacement of public-facing content, and further lateral movement into internal networks if phpMyFAQ serves as a gateway or contains integrations with other systems.
This vulnerability aligns closely with CWE-287 Improper Authentication, where the software does not adequately verify credentials before granting access to restricted resources. Furthermore, it relates to CWE-306 Missing Authentication for Critical Function, as the critical function of verifying identity is performed without ensuring prior authentication steps were completed. In terms of MITRE ATT&CK framework mapping, this behavior facilitates Initial Access via Valid Accounts and specifically exploits weaknesses in Multi-Factor Authentication implementation, allowing attackers to bypass security controls designed to protect against credential theft or phishing attacks that might otherwise be mitigated by the second factor.
Mitigation strategies focus primarily on upgrading to version 4.1.6 or later, where developers have addressed this flaw by binding TOTP verification strictly to a session established only after successful password authentication. This ensures that the two-factor check is merely an additional layer of validation rather than a standalone entry point. Additionally, the patched versions implement rate limiting for failed TOTP attempts, which significantly raises the cost and time required for brute-force attacks against the six-digit codes. For organizations unable to immediately upgrade, there are no official workarounds documented; therefore, network-level controls such as Web Application Firewalls (WAFs) may be employed temporarily to restrict access to the authentication endpoints based on IP reputation or behavioral analysis until a patch can be applied. Regular security audits and adherence to secure coding standards that mandate strict state management in authentication flows are recommended to prevent similar issues in future development cycles.