CVE-2026-1557: WP Responsive Images Path Traversal Flaw

CVE-2026-1557 Overview

The WP Responsive Images plugin for WordPress is vulnerable to a Path Traversal vulnerability (CWE-22) in all versions up to and including 1.0. The vulnerability exists in the src parameter, which fails to properly sanitize user input. This security flaw enables unauthenticated attackers to read arbitrary files from the server by manipulating file path references to access files outside the intended directory structure.

Critical Impact

Unauthenticated attackers can exploit this path traversal flaw to read sensitive files from the server, potentially exposing database credentials, configuration files, WordPress secret keys, and other confidential information without requiring any authentication.

Affected Products

• WP Responsive Images plugin for WordPress version 1.0 and earlier
• WordPress installations with WP Responsive Images plugin enabled
• Affected files include SBOutputFile.php, WPResponsiveImages.php, and image_handler.php

Discovery Timeline

• 2026-02-26 - CVE-2026-1557 published to NVD
• 2026-02-26 - Last updated in NVD database

Technical Details for CVE-2026-1557

Vulnerability Analysis

This path traversal vulnerability allows remote attackers to escape the web application's document root and access arbitrary files on the server's filesystem. The vulnerability is accessible over the network without requiring authentication, making it particularly dangerous for WordPress sites running the affected plugin.

The flaw resides in how the plugin processes the src parameter across multiple PHP files. When a user supplies a malicious path containing directory traversal sequences (such as ../), the application fails to validate or sanitize this input before using it in file operations. This allows attackers to navigate up the directory tree and read any file that the web server process has permission to access.

Common targets for exploitation include the WordPress configuration file (wp-config.php), which contains database credentials and authentication keys, as well as system files like /etc/passwd on Linux systems.

Root Cause

The root cause of this vulnerability is improper input validation in the src parameter handling within the WP Responsive Images plugin. The vulnerable code paths exist in multiple files:

• SBOutputFile.php (line 33)
• WPResponsiveImages.php (line 265)
• image_handler.php (line 28)

The plugin fails to implement proper path canonicalization or restrict file access to the intended upload directory. Without validation to strip or reject directory traversal sequences, user-controlled input can be used to construct file paths pointing to sensitive system or application files.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can craft HTTP requests with manipulated src parameter values containing path traversal sequences. By including sequences like ../ repeatedly, the attacker can traverse out of the WordPress uploads directory and access files elsewhere on the filesystem.

For example, an attacker might attempt to access the WordPress configuration file by traversing multiple directory levels upward from the plugin's intended file path, then targeting wp-config.php which contains database credentials and authentication secrets.

The Wordfence vulnerability report provides additional technical details about this vulnerability. The affected source code can be reviewed in the WordPress Plugin Trac repository.

Detection Methods for CVE-2026-1557

Indicators of Compromise

• HTTP requests to the WP Responsive Images plugin endpoints containing ../ sequences in the src parameter
• Access log entries showing requests for image_handler.php, SBOutputFile.php, or WPResponsiveImages.php with suspicious path patterns
• Unusual file access attempts targeting wp-config.php, /etc/passwd, or other sensitive files through the plugin
• Error logs indicating file access attempts outside the WordPress directory structure

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block requests containing directory traversal sequences (../, ..%2f, %2e%2e/)
• Monitor web server access logs for suspicious patterns in requests to the WP Responsive Images plugin endpoints
• Deploy intrusion detection signatures specifically targeting path traversal attempts against WordPress plugins
• Use file integrity monitoring to detect unauthorized access to sensitive configuration files

Monitoring Recommendations

• Enable detailed logging for all requests to the wp-content/plugins/wp-responsive-images/ directory
• Set up alerts for HTTP requests containing encoded or plain-text directory traversal patterns
• Monitor for abnormal file read operations by the web server process, especially outside the web root
• Review access logs regularly for signs of reconnaissance or exploitation attempts targeting this plugin

How to Mitigate CVE-2026-1557

Immediate Actions Required

• Immediately disable or remove the WP Responsive Images plugin from all WordPress installations until a patched version is available
• Review web server access logs for any evidence of exploitation attempts or successful file access
• Rotate all sensitive credentials that may have been exposed, including database passwords and WordPress authentication keys
• Implement WAF rules to block path traversal attempts at the network perimeter

Patch Information

At the time of publication, no patched version has been confirmed. Organizations should monitor the WordPress Plugin Directory and the Wordfence vulnerability report for updates regarding security fixes.

Workarounds

• Remove or deactivate the WP Responsive Images plugin entirely until a security patch is released
• Implement server-level access controls to restrict file operations within the WordPress directory
• Use a Web Application Firewall to filter requests containing path traversal sequences
• Consider implementing PHP open_basedir restrictions to limit file access scope for the web server

# Configuration example - Apache mod_rewrite rule to block path traversal attempts
# Add to WordPress .htaccess file

RewriteEngine On
RewriteCond %{QUERY_STRING} (\.\./|\.\.\\) [NC,OR]
RewriteCond %{QUERY_STRING} (\.\.%2f|\.\.%5c) [NC]
RewriteRule ^wp-content/plugins/wp-responsive-images/.* - [F,L]