CVE-2024-6694: WP Mail SMTP Information Disclosure Flaw

CVE-2024-6694 Overview

CVE-2024-6694 is an information exposure vulnerability affecting the WP Mail SMTP plugin for WordPress in all versions up to and including 4.0.1. The vulnerability stems from the plugin displaying the SMTP password in plaintext within the SMTP Password field when administrators view the plugin settings. This security weakness falls under CWE-257 (Storing Passwords in a Recoverable Format).

While this vulnerability requires administrative-level access to exploit, it presents a significant risk in scenarios where an administrator account has been compromised. An attacker with access to a compromised admin account could retrieve SMTP server credentials, potentially enabling lateral movement or unauthorized access to email infrastructure.

Critical Impact

Authenticated attackers with administrative access can view plaintext SMTP passwords, potentially enabling credential theft and lateral movement to email server infrastructure.

Affected Products

• WP Mail SMTP plugin for WordPress versions up to and including 4.0.1

Discovery Timeline

• 2024-07-20 - CVE-2024-6694 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-6694

Vulnerability Analysis

This vulnerability is classified as an information exposure issue rooted in improper credential handling. The WP Mail SMTP plugin fails to properly mask or protect SMTP password values when rendering the settings page in the WordPress admin interface. Instead of displaying an obfuscated placeholder or asterisks, the actual password is exposed in the form field.

The vulnerability exists in the OptionsAbstract.php file within the plugin's Provider options handling. When administrators access the plugin settings page, the SMTP password is retrieved from the database and rendered directly in the HTML form field, making it visible to anyone with access to the admin panel.

The attack scenario requires an adversary to first compromise an administrator account through other means (phishing, credential stuffing, session hijacking, etc.). Once authenticated with admin privileges, the attacker can navigate to the WP Mail SMTP settings and retrieve the plaintext SMTP credentials.

Root Cause

The root cause is the storage and display of SMTP passwords in a recoverable format (CWE-257). The plugin's options handling code does not implement proper password masking when rendering the settings form. This design flaw allows the password to be visible in the HTML source and potentially accessible via JavaScript on the page.

Sensitive credentials should never be displayed back to users in plaintext, even to administrators. Best practices dictate using placeholder values (such as asterisks) while allowing users to enter new passwords if changes are needed.

Attack Vector

The attack vector is network-based and requires high privileges (administrative access). The exploitation flow involves:

1. An attacker first compromises a WordPress administrator account through a separate attack vector
2. The attacker navigates to the WP Mail SMTP plugin settings page in the WordPress admin dashboard
3. The SMTP password is visible in the password input field or page source
4. The attacker extracts these credentials for use in further attacks against the organization's email infrastructure

The vulnerability mechanism centers on improper credential display in the plugin's settings interface. When the settings page loads, the stored SMTP password is retrieved and rendered in the form field without proper masking. For technical implementation details, refer to the WordPress Changeset Update that addresses this issue.

Detection Methods for CVE-2024-6694

Indicators of Compromise

• Unexpected access to WP Mail SMTP settings pages from unfamiliar IP addresses or user accounts
• Suspicious administrator login activity followed by navigation to plugin configuration pages
• Unauthorized changes to SMTP configuration or email sending patterns
• Failed login attempts to SMTP servers using previously configured credentials from unknown sources

Detection Strategies

• Monitor WordPress admin activity logs for access to WP Mail SMTP settings pages
• Implement alerting on administrator account logins from unusual locations or at unusual times
• Review email server authentication logs for suspicious login attempts using WordPress-configured SMTP credentials
• Deploy web application firewalls (WAF) to detect and log access patterns to plugin settings URLs

Monitoring Recommendations

• Enable comprehensive WordPress audit logging covering all plugin settings access
• Configure SMTP server logging to capture authentication attempts and correlate with WordPress activity
• Implement session monitoring for administrator accounts to detect potential account takeover
• Set up alerts for multiple admin panel accesses within short time windows

How to Mitigate CVE-2024-6694

Immediate Actions Required

• Update the WP Mail SMTP plugin to version 4.1.0 or later immediately
• Rotate all SMTP credentials that may have been exposed through this vulnerability
• Audit administrator account access logs for any suspicious activity
• Review and restrict the number of users with administrative access to WordPress

Patch Information

The vulnerability has been addressed in the WP Mail SMTP plugin. The fix is documented in the WordPress Changeset Update which modifies the OptionsAbstract.php file to properly mask SMTP passwords in the settings interface. Users should update to the latest version of the plugin through the WordPress admin dashboard or by downloading from the official WordPress plugin repository.

Additional vulnerability details are available in the Wordfence Vulnerability Report.

Workarounds

• If immediate patching is not possible, restrict administrative access to trusted personnel only
• Consider using WordPress security plugins to implement additional authentication factors for admin accounts
• Use environment variables or WordPress constants for SMTP configuration instead of storing credentials in the database
• Implement IP-based access restrictions for the WordPress admin panel

# Restrict WordPress admin access by IP in .htaccess
<Files wp-login.php>
    Order Deny,Allow
    Deny from all
    Allow from 192.168.1.0/24
    Allow from 10.0.0.0/8
</Files>