CVE-2026-76213 in phpMyFAQ
Summary
by MITRE • 08/19/2026
phpMyFAQ before 4.1.7 contains a brute-force vulnerability in the two-factor authentication step where the failure counter is session-scoped and reset on each successful password re-authentication. Attackers with a valid password can bypass the five-attempt limit by obtaining a fresh session cookie and repeatedly re-authenticating to reset the counter, enabling unbounded TOTP code guessing.
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Analysis
by VulDB Data Team • 08/19/2026
The vulnerability identified in phpMyFAQ versions prior to 4.1.7 represents a critical failure in the implementation of multi-factor authentication controls, specifically targeting the brute-force protection mechanisms associated with Time-based One-Time Passwords or similar second factors. This flaw stems from an incorrect scope and lifecycle management of the security counter used to track failed login attempts. In secure authentication systems, rate-limiting counters are typically designed to persist across sessions for a specific user identity or account until they expire after a set duration or reach a maximum threshold that triggers a lockout. However, in this affected version, the failure counter is scoped strictly to the current server-side session rather than being tied permanently to the authenticated user's credentials. This architectural decision creates a significant gap between the intended security policy and its actual enforcement, allowing attackers to circumvent protective measures through simple session manipulation techniques.
The operational mechanics of this exploit rely on the behavior of HTTP sessions during re-authentication processes. When an attacker possesses valid primary credentials for a target account, they can initiate a login sequence that requires secondary authentication via TOTP or another two-factor method. If the initial attempt fails due to an incorrect code, the system increments the failure counter within the current session context. Crucially, if the user subsequently re-authenticates with their correct password and primary credentials, the application resets this specific session-scoped counter back to zero. An attacker can exploit this by repeatedly obtaining fresh sessions or triggering re-authentication cycles after each failed two-factor attempt. By cycling through valid password authentications followed by single TOTP guesses, the attacker effectively neutralizes the lockout mechanism that is designed to prevent automated guessing attacks. This allows for unbounded brute-force attempts against the second factor without ever being blocked by the system's default five-attempt limit.
From a technical perspective, this vulnerability aligns with CWE-307 Improper Restriction of Excessive Authentication Attempts and CWE-613 Insufficient Session Expiration. The root cause lies in the application logic failing to associate the brute-force protection state with the user identity itself rather than transient session data that can be manipulated or reset by legitimate-looking actions like password re-entry. This misconfiguration undermines the fundamental purpose of rate limiting, which is to increase the cost and time required for an attacker to guess credentials. By resetting the counter upon successful primary authentication, the system inadvertently provides a free pass for each new guessing attempt, provided the attacker knows the username and password. This transforms what should be a high-friction barrier into a low-effort target for automated scripts or manual attackers with valid account details.
The impact of this vulnerability is severe in environments where two-factor authentication is deployed to protect sensitive administrative interfaces or user data. Although phpMyFAQ is primarily a content management system, it often hosts personal information, contact lists, and potentially other proprietary data depending on the deployment context. An attacker who successfully guesses the TOTP code gains full access to the account with all associated privileges. This bypasses one of the primary layers of defense in modern security architectures, rendering the two-factor authentication feature effectively useless for those accounts where attackers have obtained passwords through phishing, credential stuffing, or other means. The ability to perform unbounded guessing significantly reduces the time required to compromise an account from days or weeks to mere minutes, depending on the complexity and length of the TOTP code used by the application.
Mitigation strategies must address both the immediate technical flaw and broader authentication architecture principles. For administrators using affected versions, upgrading to phpMyFAQ version 4.1.7 or later is the primary remediation step as it corrects the session handling logic for failure counters. In cases where an upgrade is not immediately feasible, temporary mitigations may include implementing external rate-limiting at the web server or reverse proxy level that tracks attempts based on IP address and username combination rather than relying solely on application-level session variables. Additionally, enforcing longer TOTP codes or switching to more robust second factors such as hardware security keys can increase the difficulty of successful guessing attacks even if the brute-force limit is bypassed. Security teams should also audit other authentication modules within their applications to ensure that failure counters are consistently scoped to user identities and persist appropriately across session boundaries to prevent similar logic flaws in future implementations.