CVE-2026-76213 Overview
CVE-2026-76213 is a brute-force vulnerability in phpMyFAQ versions before 4.1.7. The flaw resides in the two-factor authentication (2FA) step, where the failure counter is session-scoped and reset on each successful password re-authentication. An attacker who already holds a valid username and password can bypass the five-attempt lockout by obtaining a fresh session cookie and repeatedly re-authenticating. This action resets the counter and allows unbounded Time-based One-Time Password (TOTP) code guessing. The weakness is tracked under [CWE-307: Improper Restriction of Excessive Authentication Attempts].
Critical Impact
Attackers with valid credentials can brute-force the second authentication factor without limit, defeating 2FA protection on phpMyFAQ accounts including administrators.
Affected Products
- phpMyFAQ versions prior to 4.1.7
- phpMyFAQ instances with two-factor authentication enabled
- Self-hosted phpMyFAQ deployments exposed to the network
Discovery Timeline
- 2026-08-19 - CVE-2026-76213 published to NVD
- 2026-08-19 - Last updated in NVD database
Technical Details for CVE-2026-76213
Vulnerability Analysis
phpMyFAQ enforces a five-attempt limit on the TOTP verification step during login. The limit is intended to block brute-force guessing of the six-digit second factor. However, the failure counter is stored in the user's session and is reset whenever password re-authentication succeeds. This design assumption breaks when an attacker treats each session as disposable. By discarding the session after five failed TOTP attempts and starting a new one, the attacker restores a clean counter and continues guessing. The attacker already possesses the valid password, so re-authentication succeeds every time. Over enough iterations, guessing a six-digit TOTP becomes feasible, collapsing the second factor to a probabilistic barrier rather than an authentication control.
Root Cause
The root cause is improper restriction of excessive authentication attempts [CWE-307]. Rate limiting must be scoped to a stable identifier such as the user account or source address, not to an attacker-controlled session cookie. Because the counter lives in session state, the attacker controls its lifetime and can reset it at will.
Attack Vector
Exploitation requires network access to the phpMyFAQ login endpoint and knowledge of a valid password. The attacker submits credentials, receives a session cookie, then issues five TOTP guesses. On the sixth attempt the account is not locked; instead, the attacker discards the session, requests a new one, replays the password, and resumes guessing. Automation scripts can iterate this loop across all one million TOTP values until a match is found. No user interaction is required beyond initial credential compromise. See the GitHub Security Advisory and the VulnCheck Security Advisory for technical details.
Detection Methods for CVE-2026-76213
Indicators of Compromise
- High volumes of POST requests to the phpMyFAQ login endpoint from a single source IP within a short window.
- Repeated successful password authentications followed by multiple failed TOTP submissions for the same user account.
- Bursts of new session cookies issued to a single client without corresponding legitimate browser activity.
- Successful 2FA logins preceded by hundreds or thousands of failed TOTP attempts across rotating sessions.
Detection Strategies
- Correlate authentication events by username and source IP rather than by session identifier to surface counter-reset behavior.
- Alert when a single account experiences more than five failed TOTP attempts across multiple sessions within a defined window.
- Baseline normal login velocity per user and flag deviations that suggest automated re-authentication loops.
Monitoring Recommendations
- Ingest phpMyFAQ web server access logs and application authentication logs into a centralized platform for correlation.
- Monitor rate of session creation per source IP and per user account, alerting on anomalous spikes.
- Track failed TOTP attempt totals per user across all sessions, not per session, to enforce a true global limit.
How to Mitigate CVE-2026-76213
Immediate Actions Required
- Upgrade all phpMyFAQ installations to version 4.1.7 or later without delay.
- Rotate administrator passwords on any instance that was exposed and running a vulnerable version.
- Review authentication logs for signs of brute-force activity against 2FA-protected accounts.
- Restrict access to the phpMyFAQ administrative interface to trusted networks where operationally feasible.
Patch Information
phpMyFAQ 4.1.7 remediates CVE-2026-76213 by moving the TOTP failure counter out of session scope and enforcing the limit against a stable account identifier. Administrators should upgrade using the official release from the phpMyFAQ project. See the GitHub Security Advisory GHSA-f98m-hcjv-7rp9 for release notes and upgrade guidance.
Workarounds
- Place phpMyFAQ behind a Web Application Firewall (WAF) with rate limiting on the login and 2FA endpoints keyed to source IP and username.
- Enforce network-layer access controls, such as VPN or IP allowlists, in front of the phpMyFAQ login page until patching is complete.
- Reduce password reuse risk by requiring unique, high-entropy passwords for all phpMyFAQ accounts, since the attack depends on a valid password.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
