CVE-2025-26763: MetaSlider Object Injection Vulnerability

CVE-2025-26763 Overview

CVE-2025-26763 is a critical Deserialization of Untrusted Data vulnerability affecting the MetaSlider Responsive Slider plugin for WordPress. This security flaw enables attackers to perform PHP Object Injection attacks against vulnerable WordPress installations. The vulnerability exists in MetaSlider versions from the initial release through version 3.94.0, potentially exposing thousands of WordPress websites to remote exploitation.

Critical Impact

This PHP Object Injection vulnerability allows unauthenticated attackers to inject arbitrary PHP objects into the application, potentially leading to remote code execution, data exfiltration, or complete site compromise depending on available gadget chains.

Affected Products

• MetaSlider Responsive Slider plugin versions through 3.94.0
• WordPress installations running vulnerable MetaSlider versions
• Websites utilizing the Slider, Gallery, and Carousel functionality provided by MetaSlider

Discovery Timeline

• 2025-02-22 - CVE-2025-26763 published to NVD
• 2025-02-22 - Last updated in NVD database

Technical Details for CVE-2025-26763

Vulnerability Analysis

This vulnerability stems from improper handling of serialized data within the MetaSlider plugin. When the application deserializes user-controlled input without adequate validation, it creates an opportunity for attackers to inject malicious PHP objects. The deserialization process reconstructs these objects, triggering their magic methods (such as __wakeup(), __destruct(), or __toString()) which can execute arbitrary code or perform other malicious actions.

The attack requires no authentication and can be exploited over the network, making it particularly dangerous for publicly accessible WordPress sites. Successful exploitation depends on the presence of suitable "gadget chains" within the WordPress installation—classes with exploitable magic methods that can be chained together to achieve code execution or other malicious outcomes.

Root Cause

The root cause is classified under CWE-502 (Deserialization of Untrusted Data). The MetaSlider plugin fails to properly sanitize or validate serialized data before passing it to PHP's deserialization functions. This allows attackers to craft malicious serialized payloads containing arbitrary PHP objects that are instantiated when the data is deserialized.

Attack Vector

The attack is network-based and can be conducted without authentication. An attacker crafts a malicious serialized PHP object payload targeting the vulnerable MetaSlider functionality. When this payload is processed by the plugin, the serialized data is deserialized, instantiating the attacker-controlled objects.

The exploitation typically follows this pattern:

1. Attacker identifies a WordPress site running vulnerable MetaSlider versions
2. Attacker identifies available POP (Property-Oriented Programming) chains in the target environment
3. Attacker crafts a serialized payload containing malicious objects
4. The payload is submitted to the vulnerable endpoint
5. MetaSlider deserializes the payload without validation
6. Magic methods are triggered during deserialization, executing the attacker's payload

For detailed technical information about this vulnerability, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-26763

Indicators of Compromise

• Unexpected serialized data patterns in HTTP request logs, particularly containing PHP object notation (e.g., O: followed by class names)
• Unusual file system activity or new files created in WordPress directories
• Web server logs showing suspicious POST requests to MetaSlider endpoints
• Unexpected outbound network connections from the WordPress server

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block serialized PHP object patterns in incoming requests
• Monitor WordPress error logs for deserialization-related errors or warnings
• Deploy endpoint detection solutions to identify post-exploitation activity such as webshell deployment
• Use vulnerability scanning tools to identify WordPress installations running MetaSlider version 3.94.0 or earlier

Monitoring Recommendations

• Enable detailed logging for all WordPress plugin activity and HTTP requests
• Set up alerts for suspicious file modifications within the wp-content/plugins/ml-slider/ directory
• Monitor for unusual database queries that could indicate data exfiltration attempts
• Implement integrity monitoring for critical WordPress core and plugin files

How to Mitigate CVE-2025-26763

Immediate Actions Required

• Update MetaSlider plugin to the latest patched version immediately
• Audit WordPress installations to identify all instances running vulnerable MetaSlider versions
• Review web server logs for indicators of exploitation attempts
• Consider temporarily disabling the MetaSlider plugin until the update can be applied

Patch Information

Website administrators should update the MetaSlider Responsive Slider plugin to a version newer than 3.94.0. The update can be applied through the WordPress admin dashboard under Plugins > Installed Plugins, or via WP-CLI using the command wp plugin update ml-slider. For detailed patch information, consult the Patchstack Vulnerability Report.

Workarounds

• Temporarily deactivate the MetaSlider plugin if an immediate update is not possible
• Implement WAF rules to block requests containing serialized PHP object patterns
• Restrict access to WordPress admin and plugin endpoints using IP allowlisting
• Consider using a managed WordPress hosting provider with built-in security controls

# Configuration example
# Update MetaSlider via WP-CLI
wp plugin update ml-slider --path=/var/www/html

# Verify current plugin version
wp plugin get ml-slider --field=version --path=/var/www/html

# Temporarily deactivate if update is not available
wp plugin deactivate ml-slider --path=/var/www/html