CVE-2025-39410 Overview
A critical PHP Object Injection vulnerability exists in the Smart Sections Theme Builder - WPBakery Page Builder Addon plugin for WordPress developed by themegusta. This insecure deserialization vulnerability allows attackers to inject malicious serialized PHP objects that, when unserialized by the application, can lead to arbitrary code execution, data manipulation, or complete site compromise.
The vulnerability stems from improper handling of user-supplied serialized data without adequate validation or sanitization. Attackers can exploit this flaw remotely without authentication, making it particularly dangerous for WordPress installations using this plugin.
Critical Impact
Unauthenticated attackers can exploit this PHP Object Injection vulnerability to achieve remote code execution, potentially leading to complete WordPress site takeover, data theft, and persistent backdoor installation.
Affected Products
- Smart Sections Theme Builder - WPBakery Page Builder Addon versions up to and including 1.7.8
- WordPress installations utilizing the affected plugin
- WPBakery Page Builder environments with the Smart Sections addon enabled
Discovery Timeline
- 2025-05-19 - CVE-2025-39410 published to NVD
- 2025-05-21 - Last updated in NVD database
Technical Details for CVE-2025-39410
Vulnerability Analysis
This vulnerability is classified as CWE-502 (Deserialization of Untrusted Data), representing a severe class of flaws that occur when applications deserialize data from untrusted sources without proper validation. In the context of PHP and WordPress, this manifests as PHP Object Injection.
When the Smart Sections Theme Builder plugin processes user-controlled input through PHP's unserialize() function, it instantiates objects based on the serialized data. If the application contains classes with magic methods such as __wakeup(), __destruct(), or __toString(), attackers can chain these methods to achieve arbitrary code execution or other malicious outcomes.
The attack can be executed remotely over the network with no prerequisites—no authentication, no user interaction, and low attack complexity. This makes it trivially exploitable for threat actors scanning for vulnerable WordPress installations.
Root Cause
The root cause of CVE-2025-39410 lies in the plugin's failure to validate or sanitize serialized data before passing it to PHP's unserialize() function. The plugin accepts user-supplied input that contains serialized PHP objects and directly deserializes this data, trusting its integrity.
When combined with existing PHP classes that have exploitable magic methods (known as "gadget chains"), this allows attackers to manipulate the application's control flow. Common WordPress and plugin class libraries often contain such gadget chains that can be leveraged for code execution.
Attack Vector
The attack is network-based and can be executed by any unauthenticated remote attacker. The exploitation workflow typically follows these steps:
- Reconnaissance: Attacker identifies WordPress sites running the vulnerable Smart Sections Theme Builder plugin version 1.7.8 or earlier
- Payload Crafting: Attacker constructs a malicious serialized PHP object payload, often leveraging known gadget chains from WordPress core or common plugins
- Delivery: The crafted payload is submitted to the vulnerable endpoint that processes serialized data
- Execution: Upon deserialization, the malicious object instantiates and executes the attacker's code through magic method invocation
- Post-Exploitation: Attacker establishes persistence, exfiltrates data, or pivots to other systems
The vulnerability typically exploits endpoints that accept serialized data through POST parameters, cookies, or other user-controllable input vectors. Technical details regarding the specific vulnerable endpoint can be found in the Patchstack WordPress Vulnerability Advisory.
Detection Methods for CVE-2025-39410
Indicators of Compromise
- Unexpected PHP serialized strings in HTTP request logs containing O: object notation patterns
- Creation of unfamiliar PHP files in wp-content/uploads/ or plugin directories
- Suspicious outbound network connections from the web server
- Modified .htaccess files or unexpected wp-config.php changes
- New administrator accounts created without authorization
Detection Strategies
- Monitor HTTP request logs for payloads containing serialized PHP object patterns (e.g., O:[0-9]+:"[a-zA-Z_]+":)
- Implement Web Application Firewall (WAF) rules to detect and block PHP object injection attempts
- Use file integrity monitoring to detect unauthorized modifications to WordPress core and plugin files
- Deploy SentinelOne Singularity to detect post-exploitation behaviors including webshell deployment and suspicious process spawning
Monitoring Recommendations
- Enable verbose logging for WordPress and review wp-content/debug.log for deserialization errors
- Implement centralized log collection with alerting for anomalous patterns
- Monitor for new file creations in WordPress directories, particularly PHP files
- Track outbound connections from the web server to identify command-and-control communications
How to Mitigate CVE-2025-39410
Immediate Actions Required
- Audit WordPress installations to identify instances of Smart Sections Theme Builder - WPBakery Page Builder Addon version 1.7.8 or earlier
- Consider temporarily disabling the plugin if a patched version is not yet available
- Implement WAF rules to block requests containing serialized PHP object patterns
- Review recent access logs for signs of exploitation attempts
- Scan WordPress installations for indicators of compromise including backdoors and unauthorized administrator accounts
Patch Information
Organizations should monitor the Patchstack WordPress Vulnerability Advisory for updated patch information from themegusta. As this vulnerability affects versions through 1.7.8, users should update to any version released after this advisory that addresses the PHP Object Injection flaw.
Verify the integrity of any updates by checking plugin signatures and reviewing changelogs for explicit mentions of security fixes addressing deserialization or object injection vulnerabilities.
Workarounds
- Disable the Smart Sections Theme Builder plugin until a patched version is available
- Implement server-level PHP configuration to disable dangerous functions using disable_functions directive in php.ini
- Deploy a WAF with rules specifically targeting PHP object injection patterns
- Restrict access to WordPress admin endpoints using IP whitelisting where feasible
- Consider using virtual patching solutions that can intercept and neutralize malicious serialized payloads
# WordPress plugin status check and disable command
wp plugin list --status=active | grep -i "smart-sections"
wp plugin deactivate visucom-smart-sections
# PHP configuration hardening (add to php.ini)
# disable_functions = system, exec, shell_exec, passthru, popen, proc_open
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
