CVE-2025-53256

Executive Summary

CVE-2025-53256 is a critical SQL Injection vulnerability discovered in the YaySMTP plugin for WordPress, developed by YayCommerce. The vulnerability resides in the improper neutralization of special elements used in an SQL command, allowing an unauthenticated attacker to inject arbitrary SQL queries. This flaw affects all versions of YaySMTP up to and including 2.6.6. Given that YaySMTP is a WordPress plugin, this vulnerability is specifically tied to the WordPress ecosystem and does not involve Apache or Nginx directly. The CVSS score of 7.6 (High) reflects the potential for complete compromise of the underlying database, including data exfiltration, modification, or deletion. No public proof-of-concept (PoC) or patch details are currently available, but the risk is elevated due to the widespread use of WordPress and the plugin's role in handling email functionality.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed through the official WordPress plugin repository and third-party marketplaces. Organizations using YaySMTP should immediately assess their exposure, as the plugin may be bundled in managed WordPress hosting environments or custom deployments. The lack of a patch increases supply chain risk, as attackers may target this vector for initial access or lateral movement within WordPress 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 (AV): Network – The vulnerability can be exploited remotely over the network.
• Attack Complexity (AC): Low – No special conditions or complex attack sequences are required.
• Privileges Required (PR): None – No authentication is needed to exploit the flaw.
• User Interaction (UI): None – The victim does not need to perform any action.
• Scope (S): Unchanged – The vulnerable component and the impacted component are the same.
• Confidentiality (C): High – Full database read access is possible.
• Integrity (I): High – Database records can be modified or deleted.
• Availability (A): High – Database availability can be impacted via destructive queries.

Threat Level: Critical due to the unauthenticated nature, low complexity, and potential for full database compromise. The EPSS score of 0.0% suggests low exploitation probability currently, but this may change as details emerge.

Deep Dive & Mechanics

The vulnerability is a classic SQL Injection (CWE-89) in the YaySMTP plugin. The plugin likely fails to sanitize user-supplied input before incorporating it into SQL queries. Common injection points include:

• SMTP configuration parameters (e.g., host, port, username, password fields)
• Log viewing or search functionality that queries the database
• AJAX endpoints that process user input without proper escaping

The injection occurs when special characters (e.g., single quotes, double quotes, semicolons) are not neutralized, allowing an attacker to break out of the intended SQL syntax and execute arbitrary commands. For example, a vulnerable parameter might be concatenated directly into a query like:

SELECT * FROM wp_options WHERE option_name = '$user_input'

An attacker could input ' OR '1'='1 to retrieve all records.

Given the plugin's role in email handling, the injection could also target tables storing email logs, credentials, or other sensitive data. The lack of authentication requirements amplifies the risk, as any visitor to the WordPress site can trigger the vulnerability.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on common SQL injection fixes.

Vulnerable Code (PHP example):

$host = $_POST['smtp_host'];
$query = "SELECT * FROM wp_yaysmtp_settings WHERE host = '$host'";
$result = $wpdb->get_results($query);

Patched Code (using prepared statements):

$host = $_POST['smtp_host'];
$query = $wpdb->prepare("SELECT * FROM wp_yaysmtp_settings WHERE host = %s", $host);
$result = $wpdb->get_results($query);

The patched version uses $wpdb->prepare() to safely bind parameters, preventing injection. Until an official patch is released, users must rely on virtual patching or disabling the plugin.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Deploy a WordPress instance with YaySMTP <= 2.6.6 installed and activated.
2. Identify injection points by fuzzing plugin parameters (e.g., via Burp Suite or custom scripts).
3. Use a tool like sqlmap to automate exploitation:

   sqlmap -u "http://target/wp-admin/admin-ajax.php?action=yaysmtp_logs&search=test" --batch --dbs
   

Manual Exploitation Example: Assume an AJAX endpoint admin-ajax.php?action=yaysmtp_search with parameter q:

GET /wp-admin/admin-ajax.php?action=yaysmtp_search&q=test' UNION SELECT user_login,user_pass FROM wp_users-- HTTP/1.1
Host: target.com

This could extract WordPress user credentials.

No public exploit code is available at this time.

Blue Team (Defensive)

Detection:

• Monitor web server logs for SQL-like patterns in GET/POST parameters (e.g., ' OR, UNION, --).
• Deploy a Web Application Firewall (WAF) with rules to block SQL injection attempts.
• Use database activity monitoring to detect anomalous queries.

Mitigation:

• Immediately disable the YaySMTP plugin if not critical.
• Apply virtual patching via WAF (e.g., ModSecurity rule: SecRule ARGS "@detectSQLi" "id:1000,deny").
• Restrict access to WordPress admin panels via IP whitelisting or VPN.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests containing SQL keywords in parameters (e.g., UNION, SELECT, ' OR)
  • Outbound database connections from the web server to unexpected IPs
• File IOCs:
  • Modified WordPress database tables (e.g., wp_users, wp_options)
  • Suspicious entries in wp_yaysmtp_logs table
• Behavioral IOCs:
  • Unusual database load or slow queries
  • Unexpected admin user creation or privilege escalation

Detection Engineering

YARA Rule

rule CVE_2025_53256_YaySMTP_SQLi {
    meta:
        description = "Detects SQL injection attempts targeting YaySMTP plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-53256"
    strings:
        $sqli1 = /['\"]\s*(OR|AND)\s+['\"]?['\"]?\s*=/i
        $sqli2 = /UNION\s+SELECT/i
        $sqli3 = /--\s*$/m
        $plugin = /yaysmtp/i
    condition:
        any of ($sqli*) and $plugin
}

Sigma Rule

title: SQL Injection Attempt Against YaySMTP Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects SQL injection patterns in HTTP requests targeting YaySMTP
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains: 
            - 'yaysmtp'
        cs-method: 
            - 'GET'
            - 'POST'
        cs-uri-query|contains:
            - "' OR"
            - "' AND"
            - "UNION SELECT"
            - "--"
    condition: selection
falsepositives:
    - Legitimate use of special characters in email fields
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-53256 SQL Injection Attempt - YaySMTP"; flow:to_server,established; content:"yaysmtp"; http_uri; nocase; pcre:"/(\x27|\x22)\s*(OR|AND)\s+.*=|\bUNION\s+SELECT\b|--\s*$/i"; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable the YaySMTP plugin until an official patch is released.
2. Virtual Patching: Deploy WAF rules to block SQL injection patterns targeting the plugin.
3. Database Hardening: Ensure the WordPress database user has minimal privileges (e.g., no DROP or CREATE).
4. Monitoring: Enable detailed logging for web and database servers, and review logs for suspicious activity.
5. Update: Monitor the YayCommerce website or WordPress plugin repository for a patched version (expected > 2.6.6).
6. Backup: Maintain recent backups of the WordPress database and files to facilitate recovery.

Valters IT
Securing Digital Frontiers