CVE-2026-111886 in phpMyFAQ
Summary
by MITRE • 10/17/2026
phpMyFAQ from 4.2.0-alpha.2 before 4.2.0-beta lacks brute-force lockout in the removeTwofactorConfig() 2FA removal endpoint, allowing authenticated attackers to guess TOTP codes without limit. Attackers holding a hijacked session and CSRF token can repeatedly POST guesses to /api/user/remove-twofactor to permanently disable the victim's 2FA.
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Analysis
by VulDB Data Team • 10/17/2026
The vulnerability identified in phpMyFAQ versions prior to 4.2.0-beta represents a critical authentication bypass mechanism rooted in the absence of rate limiting controls on specific administrative endpoints. Specifically, the removeTwofactorConfig() function within the /api/user/remove-twofactor endpoint fails to implement brute-force protection mechanisms such as account lockouts or progressive delays after failed attempts. This architectural oversight allows an authenticated attacker who has successfully hijacked a victim's session and obtained a valid Cross-Site Request Forgery (CSRF) token to execute unlimited POST requests against this API endpoint. The primary objective of these repeated requests is not merely to guess the Time-based One-Time Password (TOTP) code required for removal, but rather to exploit the lack of constraints on the number of guesses allowed per session or time window. By leveraging a stolen session cookie and CSRF token, an attacker can automate the submission of TOTP codes until one matches, thereby successfully removing two-factor authentication from the victim's account without triggering any defensive countermeasures.
From a technical perspective, this flaw constitutes a classic example of insufficient anti-automation controls on sensitive configuration changes. The vulnerability aligns with CWE-307, which describes Improper Restriction of Excessive Authentication Attempts, as well as CWE-640, Weak Password Recovery Mechanism for Forgotten Password, in the broader context of authentication integrity. Furthermore, this attack vector maps directly to MITRE ATT&CK technique T1110.001, Brute Force: Password Guessing, and potentially T1539, Steal Web Session Cookie, given that the initial access relies on session hijacking. The lack of lockout logic means that even if a strong TOTP secret is used, the entropy can be effectively reduced to zero through exhaustive search capabilities provided by automated scripts running against the unprotected endpoint. This transforms what should be a high-entropy security control into a trivially bypassable barrier when combined with session theft and CSRF exploitation.
The operational impact of this vulnerability is severe, as it allows an attacker to completely dismantle the multi-factor authentication layer protecting user accounts. Once two-factor authentication is disabled via this method, the account reverts to single-factor authentication based solely on the password. If the victim uses a weak or compromised password, which is common in many environments, the attacker gains full persistent access to the application with elevated privileges depending on the user's role within phpMyFAQ. This can lead to unauthorized modification of knowledge base articles, theft of sensitive data stored within the FAQ system, and further lateral movement if the same credentials are reused elsewhere. The ability to disable 2FA without detection or restriction significantly lowers the barrier for persistent access and increases the window of opportunity for malicious actors to exfiltrate data or deface content before any anomaly-based intrusion detection systems might flag unusual login patterns resulting from subsequent unauthorized logins with new passwords.
Mitigation strategies must focus on implementing robust rate limiting and anti-automation controls at both the application logic level and infrastructure layer. Developers should enforce strict limits on the number of consecutive failed attempts to remove two-factor authentication, incorporating exponential backoff delays or temporary account lockouts after a defined threshold is exceeded. Additionally, re-authentication requirements for sensitive operations such as disabling 2FA can help mitigate session hijacking risks by ensuring that only users who actively provide their current credentials and TOTP code in real-time can make changes. Infrastructure-level protections should include Web Application Firewall (WAF) rules designed to detect rapid-fire POST requests to authentication-related endpoints, blocking traffic that exceeds normal behavioral baselines. Upgrading to phpMyFAQ version 4.2.0-beta or later is the primary remediation step, as these versions are expected to address this specific lack of brute-force protection in the removal endpoint.