CVE-2024-3073

Executive Summary

CVE-2024-3073 is a low-severity information exposure vulnerability affecting the Easy WP SMTP by SendLayer WordPress plugin, versions up to and including 2.3.0. The plugin exposes the SMTP password in cleartext within the SMTP Password field when viewing the plugin settings page. This flaw allows authenticated attackers with administrative-level access to retrieve the SMTP password for the configured mail server. While the immediate risk is limited due to the high privileges required, it significantly amplifies the impact of a compromised administrator account, especially in environments where the SMTP server is shared or used for other critical services.

WordPress Ecosystem Context

This vulnerability is specific to the WordPress plugin ecosystem. The issue lies in how the plugin handles and displays sensitive credentials in the admin dashboard. It does not involve the underlying web server (Apache/Nginx) or WordPress core.

CVSS Breakdown & Threat Level

• CVSS Score: 2.7 (Low)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N
• Attack Vector (AV): Network – The attacker can exploit this remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): High – Administrative-level access is needed.
• User Interaction (UI): None – No user action is required.
• Scope (S): Unchanged – The exploit does not affect other components.
• Confidentiality (C): Low – Only the SMTP password is exposed.
• Integrity (I): None – No data modification is possible.
• Availability (A): None – No service disruption.

Threat Level: Low. The vulnerability requires high privileges, but it can be leveraged in post-exploitation scenarios to pivot to other systems.

Deep Dive & Mechanics

The vulnerability exists in the plugin's settings page, specifically in the field that displays the SMTP password. The plugin fails to mask or obfuscate the password value when rendering the settings form. Instead of storing and displaying a placeholder (e.g., asterisks), it outputs the actual password in the value attribute of the input field.

Root Cause: The plugin uses esc_attr() or similar escaping functions but does not replace the actual password with a masked value before rendering. This allows anyone who can view the page source or inspect the element to see the plaintext password.

Attack Scenario:

1. An attacker gains administrative access to the WordPress dashboard (e.g., via credential stuffing, phishing, or another vulnerability).
2. The attacker navigates to the Easy WP SMTP settings page.
3. The SMTP password is visible in the password field (or in the HTML source).
4. The attacker copies the password and uses it to access the SMTP server directly, potentially sending spam, phishing emails, or accessing other services that share the same credentials.

Vulnerable vs. Patched Code

Vulnerable Code (<= 2.3.0):

// In the settings page rendering function
$smtp_password = get_option('swpsmtp_smtp_password');
echo '<input type="password" name="swpsmtp_smtp_password" value="' . esc_attr($smtp_password) . '" />';

The password is stored in plaintext and echoed directly into the value attribute.

Patched Code (Hypothetical):

// In the settings page rendering function
$smtp_password = get_option('swpsmtp_smtp_password');
$masked_password = str_repeat('*', strlen($smtp_password));
echo '<input type="password" name="swpsmtp_smtp_password" value="' . esc_attr($masked_password) . '" />';

The password is masked with asterisks before being displayed. The actual password is only sent to the server when the form is submitted.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Administrative access to a WordPress site running Easy WP SMTP <= 2.3.0.
• The SMTP server must be configured in the plugin.

Steps:

1. Log in to the WordPress admin dashboard as an administrator.
2. Navigate to Settings > Easy WP SMTP.
3. View the page source or inspect the SMTP Password field.
4. The password is visible in the value attribute of the input field.

Example using browser developer tools:

// In the browser console
document.querySelector('input[name="swpsmtp_smtp_password"]').value;

This will return the plaintext SMTP password.

Blue Team (Detection & Response)

Detection:

• Monitor for unusual access to the WordPress admin settings pages, especially the Easy WP SMTP configuration.
• Look for multiple failed login attempts followed by successful admin logins.
• Check for outbound SMTP traffic from the WordPress server to unexpected destinations.

Response:

1. Immediately change the SMTP password for the affected server.
2. Rotate any other credentials that may be shared with the SMTP password.
3. Review admin account activity logs for unauthorized access.
4. Apply the plugin update when available (currently unpatched).
5. Consider using a dedicated SMTP service with separate credentials.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/easy-wp-smtp/easy-wp-smtp.php (version <= 2.3.0)
• Log Entry: Access to /wp-admin/options-general.php?page=swpsmtp_settings by a non-admin user (if privilege escalation occurred).
• Network: SMTP traffic from the WordPress server to an IP address not in the expected allowlist.
• Credential: The SMTP password appearing in plaintext in web server logs (if debug mode is enabled).

Detection Engineering

YARA Rule

rule CVE_2024_3073_Easy_WP_SMTP_Info_Exposure {
    meta:
        description = "Detects Easy WP SMTP plugin files vulnerable to CVE-2024-3073"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-3073"
    strings:
        $smtp_password = "swpsmtp_smtp_password"
        $value_attr = /value="[^"]*"/
    condition:
        $smtp_password and $value_attr
}

Sigma Rule

title: CVE-2024-3073 - Easy WP SMTP Password Exposure
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects access to the Easy WP SMTP settings page which may expose the SMTP password.
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains: "page=swpsmtp_settings"
    condition: selection
falsepositives:
    - Legitimate admin access
level: low

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-3073 - Easy WP SMTP Settings Access"; flow:to_server,established; content:"GET"; http_method; content:"/wp-admin/options-general.php"; http_uri; content:"page=swpsmtp_settings"; http_uri; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Change SMTP Password: Immediately change the SMTP password for the affected server.
2. Review Admin Accounts: Audit all administrator accounts and remove any that are not necessary.
3. Enable Two-Factor Authentication (2FA): Add 2FA for all admin accounts to reduce the risk of credential compromise.
4. Monitor Logs: Check web server and WordPress logs for any suspicious activity.

Long-Term Fix:

• The vendor (SendLayer) has not yet released a patch. Monitor the plugin's update page for a fix.
• As a workaround, consider using a different SMTP plugin that properly masks passwords.
• Implement a Web Application Firewall (WAF) rule to block access to the settings page from non-admin IPs.

Valters IT Signature:

Valters IT
Senior DevSecOps Engineer
Cyber Threat Intelligence Expert