CVE-2026-28020: ThemeREX Chroma LFI Vulnerability

CVE-2026-28020 Overview

CVE-2026-28020 is a PHP Local File Inclusion (LFI) vulnerability affecting the ThemeREX Chroma WordPress theme. The vulnerability stems from improper control of filename parameters used in PHP include/require statements, allowing attackers to include arbitrary local files from the server's filesystem. This security flaw enables unauthorized access to sensitive server files and potentially facilitates further exploitation including remote code execution.

Critical Impact

Attackers can exploit this LFI vulnerability to read sensitive configuration files, access credentials, and potentially achieve code execution by including files with malicious content or by leveraging log poisoning techniques.

Affected Products

• ThemeREX Chroma WordPress Theme version 1.11 and earlier
• WordPress installations running vulnerable Chroma theme versions

Discovery Timeline

• 2026-03-05 - CVE CVE-2026-28020 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-28020

Vulnerability Analysis

This vulnerability falls under CWE-98 (Improper Control of Filename for Include/Require Statement in PHP Program). The ThemeREX Chroma theme fails to properly sanitize user-controlled input before passing it to PHP's file inclusion functions. When user input is incorporated into include, require, include_once, or require_once statements without adequate validation, attackers can manipulate the file path to access files outside the intended directory structure.

Local File Inclusion vulnerabilities in WordPress themes are particularly dangerous because they can expose critical WordPress configuration files such as wp-config.php, which contains database credentials, authentication keys, and other sensitive information. Additionally, attackers may chain this vulnerability with other techniques to achieve remote code execution.

Root Cause

The root cause of CVE-2026-28020 is the absence of proper input validation and sanitization on user-supplied parameters that control which files are included by PHP. The Chroma theme accepts filename or path input from users and incorporates it directly into include statements without verifying that the requested file falls within expected boundaries or matches an allowed list of files.

Attack Vector

The attack vector involves manipulating HTTP request parameters to traverse the directory structure using sequences like ../ (dot-dot-slash) or by specifying absolute paths. An attacker can craft malicious requests targeting the vulnerable theme component, supplying path traversal sequences to access files outside the web root or include sensitive configuration files.

The exploitation process typically involves:

1. Identifying the vulnerable parameter in the Chroma theme
2. Crafting a request with path traversal sequences (e.g., ../../../../etc/passwd)
3. Submitting the malicious request to read local files
4. Potentially escalating to code execution via log poisoning or PHP filter wrappers

For detailed technical analysis, refer to the Patchstack WordPress Vulnerability Report.

Detection Methods for CVE-2026-28020

Indicators of Compromise

• Unusual HTTP requests containing path traversal sequences (../, ..%2f, %2e%2e/) targeting the Chroma theme
• Web server logs showing requests for sensitive files like wp-config.php, /etc/passwd, or php://filter wrapper usage
• Unexpected file access patterns in PHP error logs indicating include failures for system files

Detection Strategies

• Monitor web application firewall (WAF) logs for path traversal patterns targeting WordPress theme directories
• Implement log analysis rules to detect requests containing PHP filter wrappers (php://filter/convert.base64-encode/resource=)
• Review access logs for requests to Chroma theme endpoints with abnormally long or encoded path parameters
• Deploy file integrity monitoring on critical WordPress configuration files

Monitoring Recommendations

• Enable verbose logging for WordPress and the web server to capture detailed request information
• Configure SIEM rules to alert on multiple LFI attempt patterns from single source IPs
• Monitor for suspicious file read operations on sensitive system and WordPress configuration files
• Implement real-time alerting for requests matching known LFI exploitation patterns

How to Mitigate CVE-2026-28020

Immediate Actions Required

• Update the ThemeREX Chroma theme to a patched version if available from the vendor
• If no patch is available, consider temporarily disabling or removing the Chroma theme
• Implement WAF rules to block path traversal sequences in requests to the WordPress installation
• Review server access logs for signs of exploitation attempts

Patch Information

Check with ThemeREX for an updated version of the Chroma theme that addresses this vulnerability. The vulnerable versions include Chroma 1.11 and earlier. Monitor the vendor's official channels and the Patchstack WordPress Vulnerability Report for patch availability announcements.

Workarounds

• Deploy a Web Application Firewall (WAF) with rules to block common LFI patterns including path traversal sequences
• Restrict PHP's open_basedir configuration to limit file access to the WordPress directory
• Disable unnecessary PHP functions that could be leveraged for exploitation (allow_url_include = Off)
• Switch to an alternative WordPress theme until a patched version of Chroma is released
• Implement strict input validation at the web server level using ModSecurity or similar tools

# Example PHP configuration hardening
# Add to php.ini or .htaccess

# Disable remote file inclusion
allow_url_include = Off
allow_url_fopen = Off

# Restrict file access to WordPress directory
open_basedir = /var/www/html/wordpress/

# Log PHP errors for monitoring
log_errors = On
error_log = /var/log/php/error.log