CVE-2025-53251: Pin WP File Upload RCE Vulnerability

CVE-2025-53251 Overview

CVE-2025-53251 is an Unrestricted Upload of File with Dangerous Type vulnerability (CWE-434) affecting the An-Themes Pin WP WordPress theme. This vulnerability allows attackers to upload a web shell to a web server, potentially leading to complete server compromise. The flaw exists in versions prior to 7.2 of the Pin WP theme.

Critical Impact

Attackers can upload malicious web shells to vulnerable WordPress installations, enabling remote code execution and full server compromise.

Affected Products

• An-Themes Pin WP theme versions prior to 7.2
• WordPress installations running vulnerable Pin WP theme versions

Discovery Timeline

• 2025-08-21 - CVE CVE-2025-53251 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2025-53251

Vulnerability Analysis

This vulnerability stems from improper file upload validation in the Pin WP WordPress theme. The theme fails to adequately restrict the types of files that can be uploaded through its file handling functionality. This oversight allows attackers to bypass intended security controls and upload files with dangerous extensions, such as PHP scripts containing malicious code.

When a web shell is successfully uploaded, the attacker gains the ability to execute arbitrary commands on the underlying server with the privileges of the web server process. This can lead to data theft, website defacement, lateral movement within the network, and establishment of persistent backdoor access.

Root Cause

The root cause of CVE-2025-53251 is the absence of proper server-side validation for uploaded file types. The Pin WP theme does not implement adequate checks to ensure that only safe file types (such as images) can be uploaded. Without proper MIME type verification, file extension validation, and content inspection, malicious files can be uploaded and subsequently executed on the server.

Attack Vector

The attack exploits the file upload functionality within the Pin WP theme. An attacker crafts a malicious PHP file containing web shell code and uploads it through the vulnerable upload mechanism. Since the theme does not properly validate file types, the malicious file is accepted and stored on the server. The attacker then accesses the uploaded web shell through a direct URL request, gaining interactive command execution capabilities on the compromised server.

The vulnerability can typically be exploited by manipulating file extensions, using double extensions, modifying MIME type headers, or embedding malicious code within files that appear legitimate. For detailed technical information, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-53251

Indicators of Compromise

• Presence of unexpected PHP files in theme upload directories
• Web server access logs showing requests to unusual file paths within the Pin WP theme directory
• New or modified files with .php, .phtml, or other executable extensions in upload folders
• Outbound network connections from the web server process to unknown external IPs

Detection Strategies

• Monitor file system changes in WordPress theme directories, particularly the wp-content/themes/pin-wp/ path
• Implement Web Application Firewall (WAF) rules to detect web shell upload attempts
• Scan for known web shell signatures and suspicious file contents using security tools
• Review web server access logs for POST requests to upload endpoints followed by GET requests to unusual file paths

Monitoring Recommendations

• Enable file integrity monitoring on WordPress installations
• Configure alerts for new executable file creations in theme directories
• Monitor for anomalous process spawning from web server processes
• Implement logging for all file upload operations with user attribution

How to Mitigate CVE-2025-53251

Immediate Actions Required

• Update the Pin WP theme to version 7.2 or later immediately
• Audit existing WordPress installations for signs of compromise
• Remove any suspicious files discovered in theme upload directories
• Review web server access logs for evidence of exploitation attempts

Patch Information

An-Themes has addressed this vulnerability in Pin WP version 7.2. Users should update to this version or later through the WordPress admin dashboard or by manually downloading and installing the patched theme from the vendor. For additional details, consult the Patchstack Vulnerability Report.

Workarounds

• Temporarily disable the Pin WP theme and switch to a known-secure theme until patching is possible
• Implement server-level restrictions to prevent PHP execution in upload directories
• Deploy a Web Application Firewall with rules to block file upload attacks
• Restrict file upload permissions at the web server configuration level

# Apache configuration to prevent PHP execution in upload directories
# Add to .htaccess in the theme's upload directory
<FilesMatch "\.(?:php|phtml|php[0-9]+)$">
    Require all denied
</FilesMatch>