CVE-2025-39592: Subscribe to Unlock Lite LFI Vulnerability

CVE-2025-39592 Overview

CVE-2025-39592 is a PHP Local File Inclusion (LFI) vulnerability in the WP Shuffle Subscribe to Unlock Lite WordPress plugin. The flaw stems from improper control of filename input passed to PHP include or require statements [CWE-98]. Attackers with low-privilege access can manipulate file path parameters to include arbitrary PHP files from the local file system. The vulnerability affects all versions of subscribe-to-unlock-lite up to and including 1.3.0. Successful exploitation can lead to disclosure of sensitive configuration data, code execution through log poisoning, or full site compromise when combined with file upload functionality.

Critical Impact
An authenticated attacker can include arbitrary local PHP files, leading to code execution, credential disclosure, and full WordPress site compromise.

Affected Products

WP Shuffle Subscribe to Unlock Lite plugin (subscribe-to-unlock-lite)
All versions from n/a through 1.3.0
WordPress sites with the vulnerable plugin installed and active

Discovery Timeline

2025-04-16 - CVE-2025-39592 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-39592

Vulnerability Analysis

The vulnerability resides in the Subscribe to Unlock Lite plugin's handling of file path parameters passed to PHP include directives. The plugin accepts user-controlled input and passes it to include, require, include_once, or require_once without proper sanitization or whitelisting. This allows an authenticated attacker to traverse the file system and load arbitrary PHP files into the execution context.

The CWE-98 classification confirms this as an improper control of filename for include/require statements. While the title references PHP Remote File Inclusion (RFI), the practical exploitation scenario is Local File Inclusion (LFI) because most production PHP installations disable allow_url_include. The EPSS score of 0.712% places this vulnerability in the 48th percentile for exploitation likelihood.

Root Cause

The root cause is missing input validation on a parameter that determines which file the plugin loads. The plugin trusts user-supplied data to construct a file path without enforcing a strict allow-list of permitted files. Path traversal sequences such as ../ can escape the intended directory, and null byte or extension-stripping tricks may bypass weak filters.

Attack Vector

The attack requires network access and low-level authenticated privileges (PR:L) on the target WordPress site. An attacker submits a crafted request to the vulnerable plugin endpoint with a manipulated file path parameter. The PHP interpreter then includes and executes the referenced file. Common exploitation paths include reading wp-config.php to extract database credentials, including session files or uploaded media containing PHP payloads, or poisoning web server logs and including them for code execution.

No verified proof-of-concept code is available. See the Patchstack Vulnerability Report for additional technical details.

Detection Methods for CVE-2025-39592

Indicators of Compromise

HTTP requests to plugin endpoints containing path traversal sequences such as ../, ..%2f, or URL-encoded variants in query parameters or POST bodies
Unexpected access to sensitive files including wp-config.php, /etc/passwd, or PHP session files in web server logs
PHP error log entries referencing include() or require() failures with attacker-controlled paths
Outbound connections from the web server to attacker infrastructure following suspicious include activity

Detection Strategies

Inspect WordPress access logs for requests targeting subscribe-to-unlock-lite plugin endpoints with suspicious file path parameters
Deploy web application firewall rules that detect directory traversal patterns and PHP wrapper schemes such as php://filter and php://input
Monitor for newly created or modified PHP files in wp-content/uploads/ that may serve as LFI payload sources
Correlate plugin-related requests with authentication events to identify low-privilege accounts being abused

Monitoring Recommendations

Enable PHP error logging and forward logs to a centralized SIEM for analysis
Implement file integrity monitoring on WordPress core files, plugin directories, and wp-config.php
Track HTTP 200 responses for plugin endpoints that should normally return errors or redirects
Alert on outbound connections initiated by the PHP-FPM or web server process to non-approved destinations

How to Mitigate CVE-2025-39592

Immediate Actions Required

Deactivate and remove the Subscribe to Unlock Lite plugin if version 1.3.0 or earlier is installed and no patched version is available
Audit WordPress user accounts and revoke unnecessary low-privilege access that could be leveraged for exploitation
Review web server and PHP logs for evidence of prior exploitation attempts targeting plugin endpoints
Rotate WordPress secrets, database credentials, and API keys stored in wp-config.php if compromise is suspected

Patch Information

At the time of publication, the vulnerability affects all versions up to and including 1.3.0. Consult the Patchstack Vulnerability Report for the latest patch availability status from the plugin maintainer.

Workarounds

Restrict access to the vulnerable plugin endpoints using web server access control rules or .htaccess directives
Set the PHP directive open_basedir to confine file system access to the WordPress installation directory
Deploy a web application firewall with rules blocking path traversal and PHP wrapper exploitation attempts
Disable allow_url_include and allow_url_fopen in php.ini to prevent remote file inclusion fallback scenarios

bash

# Configuration example: harden php.ini against file inclusion attacks
allow_url_include = Off
allow_url_fopen = Off
open_basedir = "/var/www/html:/tmp"
disable_functions = "exec,passthru,shell_exec,system,proc_open,popen"