CVE-2025-59943

Executive Summary

CVE-2025-59943 is a security vulnerability in phpMyFAQ, an open-source FAQ web application. The flaw allows an attacker to register multiple user accounts using the same email address, as the application does not enforce email uniqueness during registration. This can lead to account ambiguity, and in certain configurations, may enable privilege escalation or account takeover. The vulnerability affects versions 4.0-nightly-2025-10-03 and below, and is fixed in version 4.0.13.

Supply Chain & Package Security

phpMyFAQ is a PHP-based application. While not a package manager dependency (like NPM or PyPI), the application itself is distributed as a web application. The vulnerability is in the core registration logic, not in a third-party library. However, administrators should ensure they are using the latest patched version (4.0.13) to mitigate this risk.

CVSS Breakdown & Threat Level

• CVSS Score: 8.1 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: High (I:H)
• Availability Impact: None (A:N)

The high integrity impact stems from the potential for account takeover and privilege escalation, while the low confidentiality impact reflects the possibility of accessing account-related information.

Deep Dive & Mechanics

The vulnerability lies in the user registration process of phpMyFAQ. The application does not check for existing email addresses before creating a new account. This allows an attacker to:

1. Register multiple accounts with the same email address.
2. Exploit the fact that email is used as an identifier for password resets, notifications, and administrative actions.
3. In certain configurations, this can lead to:
   • Account Ambiguity: The system may not know which account to associate with a given email.
   • Privilege Escalation: If an admin account is created with the same email as a regular user, the attacker might gain admin privileges.
   • Account Takeover: An attacker could potentially take over an existing account by registering a new account with the same email and then using password reset functionality.

The root cause is the lack of a unique constraint on the email field in the user database table, and the absence of a server-side check during registration.

Vulnerable vs. Patched Code

Vulnerable Code (phpMyFAQ <= 4.0-nightly-2025-10-03):

The registration logic likely does not check for existing emails. A simplified example:

// Vulnerable registration code
function registerUser($email, $password) {
    // No check for existing email
    $query = "INSERT INTO users (email, password) VALUES ('$email', '$password')";
    // Execute query
}

Patched Code (phpMyFAQ 4.0.13):

The patched version adds a check for email uniqueness before inserting a new user.

// Patched registration code
function registerUser($email, $password) {
    // Check if email already exists
    $checkQuery = "SELECT id FROM users WHERE email = '$email'";
    $result = executeQuery($checkQuery);
    if (numRows($result) > 0) {
        // Email already exists, reject registration
        return false;
    }
    $query = "INSERT INTO users (email, password) VALUES ('$email', '$password')";
    // Execute query
}

Exploitation & Lab Setup

Red Team

1. Setup: Deploy a vulnerable instance of phpMyFAQ (version 4.0-nightly-2025-10-03 or earlier).
2. Exploitation Steps:
   • Navigate to the registration page.
   • Register a user with email attacker@example.com and password password1.
   • Log out.
   • Register another user with the same email attacker@example.com but a different password password2.
   • Now, two accounts exist with the same email.
   • Use the password reset feature for attacker@example.com. The system may send a reset link to the email, but the attacker can control which account gets reset.
   • If the system allows login with email and password, the attacker can try both passwords to access different accounts.
   • In a more advanced scenario, if an admin account is created with the same email, the attacker might be able to escalate privileges.

Blue Team

1. Detection:
   • Monitor for multiple registration attempts from the same IP address with different usernames but the same email.
   • Look for password reset requests followed by successful logins from different accounts with the same email.
   • Check database logs for duplicate email entries in the user table.
2. Mitigation:
   • Immediately upgrade to phpMyFAQ version 4.0.13.
   • If upgrade is not possible, implement a server-side check for email uniqueness in the registration code.
   • Add a unique constraint on the email column in the database.
   • Monitor user registration logs for anomalies.

Indicators of Compromise (IOCs)

• Network:
  • Multiple POST requests to /registration.php or similar endpoint with the same email parameter.
  • Password reset requests for the same email from different IPs.
• Host:
  • Database entries showing multiple user accounts with the same email address.
  • Log entries showing successful registrations with duplicate emails.
• File:
  • No specific file-based IOCs.

Detection Engineering

YARA Rule

rule phpmyfaq_duplicate_email_registration {
    meta:
        description = "Detects attempts to register multiple accounts with the same email in phpMyFAQ"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-59943"
    strings:
        $registration_endpoint = "/registration.php" nocase
        $email_field = "email=" nocase
        $post_method = "POST" nocase
    condition:
        all of them
}

Sigma Rule

title: phpMyFAQ Duplicate Email Registration Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects multiple registration attempts with the same email address in phpMyFAQ
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/registration.php'
        cs-uri-query|contains: 'email='
    condition: selection
    timeframe: 5m
    aggregation:
        field: cs-uri-query
        function: count
        condition: gt 1
falsepositives:
    - Legitimate users registering multiple accounts (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"phpMyFAQ Duplicate Email Registration Attempt"; flow:to_server; content:"POST"; http_method; content:"/registration.php"; http_uri; content:"email="; http_client_body; threshold:type both, track by_src, count 2, seconds 300; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Upgrade to phpMyFAQ version 4.0.13 or later.
2. Workaround: If upgrade is not possible, manually add a unique constraint on the email column in the user database table and modify the registration code to check for existing emails.
3. Long-term: Implement input validation and enforce uniqueness constraints at the application and database levels.
4. Monitoring: Enable logging for user registration and password reset events. Monitor for anomalies.

Valters IT
Securing Your Digital Frontier