CVE-2026-76214 in phpMyFAQ
Summary
by MITRE • 08/19/2026
phpMyFAQ before 4.1.7 (affected versions <= 4.1.5) fails to persist the WebAuthn login challenge generated by prepareForLogin, because neither WebAuthn controller saves the mutated key objects back to the database. At login the anti-replay comparison is skipped by its own null guard, allowing an attacker who captures a successful WebAuthn assertion to replay it indefinitely and authenticate as the user without any interaction or hardware key.
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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 authentication bypass rooted in improper state management within the WebAuthn implementation. Specifically, the flaw resides in the failure of the application to persist mutated key objects back to the database after they are generated by the prepareForLogin function. In secure cryptographic protocols such as FIDO2 and WebAuthN, maintaining an accurate record of challenge states is essential for preventing replay attacks. When the system generates a unique challenge for authentication, it must store this state securely so that subsequent verification steps can validate against it. However, due to the omission in saving these mutated key objects, the database retains stale or null values regarding the active login challenges. This architectural oversight fundamentally undermines the integrity of the authentication handshake process.
The operational impact of this flaw is severe, as it allows for indefinite replay attacks without requiring any physical interaction with hardware security keys. During the login verification phase, the system employs a null guard to check if a challenge exists before performing anti-replay comparisons. Because the challenges are not persisted, the database returns null values when the application attempts to verify the assertion submitted by the client. The presence of this null value causes the anti-replay logic to be skipped entirely rather than failing securely. Consequently, an attacker who intercepts a valid WebAuthn assertion can reuse it repeatedly to authenticate as any user whose credentials were captured. This bypasses the requirement for physical possession of the authenticator device, effectively reducing multi-factor authentication to single-factor password-based security with no additional protection against credential theft or session hijacking via replayed tokens.
From a classification perspective, this vulnerability aligns closely with CWE-284, which describes Improper Access Control, as it allows unauthorized access through flawed validation logic. Furthermore, the specific mechanism of capturing and reusing authentication data falls under MITRE ATT&CK technique T1078, Valid Accounts, specifically within the context of replaying valid credentials or tokens to gain persistent access without detection. The failure also relates to CWE-362, Concurrent Execution using Shared Resource with Improper Synchronization, insofar as the state management fails to ensure consistency between the generation and verification phases across different request cycles.
Mitigation strategies must prioritize immediate patching to version 4.1.7 or later, where the persistence layer has been corrected to save mutated key objects properly. In environments where upgrading is not immediately feasible, administrators should implement strict network-level controls such as rate limiting on authentication endpoints and enforce short-lived session tokens to reduce the window of opportunity for replay attacks. Additionally, enabling comprehensive logging and monitoring for repeated login attempts from identical source IPs or user agents can help detect ongoing exploitation activities. It is also advisable to review WebAuthn implementations across all integrated systems to ensure that challenge-response mechanisms adhere strictly to FIDO2 standards regarding state persistence and nonce validation.