CVE-2025-13587: WordPress 2FA Email Plugin Auth Bypass

CVE-2025-13587 Overview

The Two Factor (2FA) Authentication via Email plugin for WordPress contains an authentication bypass vulnerability in versions up to and including 1.9.8. The flaw exists in the SS88_2FAVE::wp_login() method, which only enforces the 2FA requirement if the token HTTP GET parameter is undefined. This implementation flaw allows attackers to completely bypass two-factor authentication by supplying any value—including an empty string—in the token parameter during the login process.

Critical Impact

Attackers with valid credentials can bypass two-factor authentication entirely, negating the security benefit of 2FA and potentially gaining unauthorized access to WordPress administrator accounts.

Affected Products

• Two Factor (2FA) Authentication via Email plugin for WordPress versions ≤ 1.9.8

Discovery Timeline

• 2026-02-19 - CVE CVE-2025-13587 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2025-13587

Vulnerability Analysis

This authentication bypass vulnerability stems from a critical flaw in how the plugin validates two-factor authentication tokens. The SS88_2FAVE::wp_login() method implements conditional logic that checks whether the token parameter exists in the HTTP GET request rather than properly validating the token's value against expected credentials. When the parameter is undefined, the plugin correctly triggers the 2FA challenge. However, when any value is provided—even an empty string—the plugin interprets this as the user having completed the 2FA process, allowing login to proceed without proper verification.

The vulnerability is classified under CWE-20 (Improper Input Validation), as the plugin fails to properly validate the authentication token input before making access control decisions. This represents a fundamental security design flaw where the presence of a parameter is conflated with its validity.

Root Cause

The root cause lies in improper input validation within the SS88_2FAVE::wp_login() method at line 218 of the plugin code. The method uses a conditional check that evaluates whether the token parameter is defined rather than verifying whether the provided token value matches the expected 2FA code sent to the user's email. This logical error allows any request containing a token parameter—regardless of its actual value—to satisfy the 2FA requirement.

Attack Vector

The attack is network-based and requires low privileges (valid WordPress credentials). An attacker who has obtained valid username and password credentials through phishing, credential stuffing, or other means can bypass the 2FA protection by simply appending ?token= or ?token=anyvalue to the login URL. This allows complete circumvention of the two-factor authentication mechanism that site administrators rely upon for enhanced account security.

The exploitation is straightforward: during the standard WordPress login flow, after providing valid credentials, the attacker can append the token parameter with any value to the request, causing the plugin to skip the email-based verification step entirely.

Detection Methods for CVE-2025-13587

Indicators of Compromise

• Login requests containing the token parameter with empty or invalid values that result in successful authentication
• Multiple successful logins from the same account without corresponding 2FA email delivery events
• Authentication logs showing logins that bypass the normal 2FA verification workflow
• Unusual login patterns from accounts protected by two-factor authentication

Detection Strategies

• Monitor web server access logs for login requests containing ?token= with empty or suspicious values
• Implement log correlation between WordPress authentication events and email 2FA token delivery
• Alert on successful logins where no corresponding 2FA email was generated or delivered
• Review authentication plugin logs for anomalies in the 2FA verification process

Monitoring Recommendations

• Enable detailed logging for WordPress authentication events including all GET parameters
• Implement real-time alerting for login attempts that include unexpected token parameter values
• Monitor for credential stuffing attacks that may precede exploitation of this vulnerability
• Track plugin version inventory across WordPress installations to identify vulnerable deployments

How to Mitigate CVE-2025-13587

Immediate Actions Required

• Update the Two Factor (2FA) Authentication via Email plugin to a version newer than 1.9.8 immediately
• Review recent authentication logs for signs of bypass attempts or unauthorized access
• Consider temporarily disabling the vulnerable plugin until patched versions can be deployed
• Implement additional security layers such as IP-based access restrictions for administrative accounts

Patch Information

A security patch addressing this vulnerability is available in the plugin changelog. Site administrators should update to the latest version of the Two Factor (2FA) Authentication via Email plugin through the WordPress plugin repository. The fix addresses the improper input validation in the SS88_2FAVE::wp_login() method to properly validate token values rather than merely checking for parameter presence.

For technical details on the vulnerability and the applied fix, refer to the WordPress Plugin Code Snippet and the WordPress Plugin Change Log. Additional vulnerability information is available in the Wordfence Vulnerability Report.

Workarounds

• Implement Web Application Firewall (WAF) rules to block login requests with empty or malformed token parameters
• Add server-level access controls to restrict WordPress admin panel access to trusted IP addresses only
• Consider using an alternative two-factor authentication plugin until the patch can be applied
• Enable additional WordPress security measures such as login attempt rate limiting and brute force protection