CVE-2025-22540: Emailing Subscription SQLi Vulnerability

CVE-2025-22540 Overview

CVE-2025-22540 is a critical SQL Injection vulnerability affecting the Emailing Subscription plugin for WordPress, developed by Sebastian Orellana. This vulnerability allows attackers to perform Blind SQL Injection attacks against vulnerable installations, potentially leading to unauthorized access to sensitive database information.

The vulnerability stems from improper neutralization of special elements used in SQL commands (CWE-89), enabling attackers to manipulate database queries through maliciously crafted input. As a blind SQL injection variant, attackers cannot directly see the results of their injected queries but can infer information through application behavior and timing-based techniques.

Critical Impact

This vulnerability allows unauthenticated remote attackers to extract sensitive data from the WordPress database, including user credentials, email addresses, and other confidential information stored by the plugin.

Affected Products

• Emailing Subscription WordPress Plugin versions through 1.4.1
• WordPress installations running vulnerable versions of the plugin
• Any website using the email-suscripcion plugin from n/a through 1.4.1

Discovery Timeline

• 2025-01-09 - CVE-2025-22540 published to NVD
• 2025-01-09 - Last updated in NVD database

Technical Details for CVE-2025-22540

Vulnerability Analysis

This Blind SQL Injection vulnerability exists within the Emailing Subscription WordPress plugin. The vulnerability allows attackers to inject malicious SQL statements through user-controllable input fields that are not properly sanitized before being incorporated into database queries.

As a network-accessible vulnerability requiring no authentication or user interaction, attackers can remotely exploit this flaw against any WordPress site running the vulnerable plugin. The attack can cross security boundaries (scope changed), primarily impacting data confidentiality with the potential for some availability impact through database manipulation.

Root Cause

The root cause of CVE-2025-22540 lies in inadequate input validation and parameterization of user-supplied data within the plugin's database query construction. When processing subscription-related requests, the plugin fails to properly sanitize or escape special SQL characters before incorporating them into database queries.

WordPress provides secure database access methods through the $wpdb class, including prepared statements that prevent SQL injection. However, this plugin appears to construct queries using raw user input without leveraging these protective mechanisms.

Attack Vector

The vulnerability is exploitable via the network (AV:N) with low attack complexity (AC:L), requiring no privileges (PR:N) and no user interaction (UI:N). Attackers can craft malicious HTTP requests containing SQL injection payloads targeting the vulnerable plugin endpoints.

In a Blind SQL Injection scenario, attackers typically employ two main techniques:

Boolean-based Blind SQL Injection: The attacker sends payloads that cause the application to return different responses based on whether the injected SQL condition evaluates to true or false, allowing character-by-character extraction of database contents.

Time-based Blind SQL Injection: The attacker uses SQL commands like SLEEP() or BENCHMARK() to cause deliberate delays in database response, inferring information based on response timing.

For technical details on this specific vulnerability, see the Patchstack Vulnerability Advisory.

Detection Methods for CVE-2025-22540

Indicators of Compromise

• Unusual or malformed HTTP requests targeting Emailing Subscription plugin endpoints
• Database query logs showing unexpected SQL syntax including UNION, SELECT, SLEEP(), or BENCHMARK() functions
• Abnormally slow response times that may indicate time-based SQL injection attempts
• Web server access logs containing common SQL injection patterns in request parameters

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block SQL injection patterns in incoming requests
• Enable WordPress audit logging to monitor for suspicious database query activity
• Implement intrusion detection signatures for common blind SQL injection payloads
• Review web server access logs for requests containing SQL metacharacters and keywords

Monitoring Recommendations

• Monitor database query execution times for anomalies that could indicate time-based exploitation
• Set up alerts for high volumes of requests to the Emailing Subscription plugin endpoints
• Track failed database queries that may indicate injection attempts being blocked
• Enable real-time monitoring of WordPress plugin activity through security plugins

How to Mitigate CVE-2025-22540

Immediate Actions Required

• Audit WordPress installations to identify any sites running the Emailing Subscription plugin
• Consider temporarily deactivating the Emailing Subscription plugin until a patched version is available
• Implement WAF rules to filter SQL injection attempts targeting the plugin
• Review database access logs for signs of prior exploitation

Patch Information

Organizations should monitor the Patchstack Vulnerability Advisory for updates regarding official patches from the plugin developer. As of the CVE publication date, versions through 1.4.1 are confirmed vulnerable.

Administrators should check the WordPress plugin repository for any security updates released after January 9, 2025, and apply them immediately upon availability.

Workarounds

• Deactivate and remove the Emailing Subscription plugin if it is not essential to site functionality
• Implement a Web Application Firewall with SQL injection protection rules
• Restrict access to WordPress admin and plugin endpoints using IP allowlisting where feasible
• Consider alternative email subscription plugins that have undergone security audits

# WordPress CLI commands to check and deactivate the vulnerable plugin
# Check if the plugin is installed
wp plugin list --name=email-suscripcion --status=active

# Deactivate the plugin as a temporary mitigation
wp plugin deactivate email-suscripcion

# Alternative: Restrict plugin access via .htaccess (Apache)
# Add to .htaccess in wp-content/plugins/email-suscripcion/
# <Files *.php>
#   Order Deny,Allow
#   Deny from all
# </Files>