CVE-2025-62016: KALLYAS Unrestricted File Upload Flaw

CVE-2025-62016 Overview

CVE-2025-62016 is a critical Unrestricted Upload of File with Dangerous Type vulnerability affecting the KALLYAS WordPress theme developed by hogash. This vulnerability allows authenticated attackers with low privileges to upload arbitrary files, including potentially malicious PHP scripts, to vulnerable WordPress installations. The flaw stems from insufficient file type validation in the theme's upload functionality, enabling attackers to bypass security controls and execute arbitrary code on the server.

Critical Impact

Attackers with low-level authentication can upload malicious files to achieve remote code execution, potentially leading to complete website compromise, data theft, and server takeover.

Affected Products

• KALLYAS WordPress Theme versions up to and including 4.22.0
• WordPress installations using vulnerable KALLYAS theme versions

Discovery Timeline

• 2025-11-06 - CVE-2025-62016 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2025-62016

Vulnerability Analysis

This vulnerability is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type), a well-known attack vector that allows threat actors to upload files containing malicious code. In the context of the KALLYAS WordPress theme, the vulnerable functionality fails to properly validate and restrict the types of files that can be uploaded through the theme's interface.

The vulnerability affects the scope beyond just the vulnerable component, meaning a successful exploit can impact resources managed by other authority components. This cross-scope impact significantly elevates the risk profile, as attackers can potentially pivot from the WordPress application to affect other systems or services on the hosting infrastructure.

Root Cause

The root cause of this vulnerability lies in improper validation of file uploads within the KALLYAS theme. The theme's upload handling mechanism does not adequately verify file extensions, MIME types, or file content before allowing uploads to be stored on the server. This insufficient validation creates an opportunity for attackers to upload files with dangerous extensions (such as .php, .phtml, or other executable formats) that can then be accessed and executed via direct URL requests.

Attack Vector

The attack is network-based and requires only low-level authentication to exploit. An attacker who has obtained any valid WordPress user account (even with minimal subscriber-level privileges) can leverage the vulnerable upload functionality to place malicious files on the target server.

The exploitation flow typically follows this pattern:

1. The attacker authenticates to the WordPress installation with any valid user credentials
2. The attacker identifies and accesses the vulnerable file upload functionality within the KALLYAS theme
3. The attacker crafts a malicious file (such as a PHP web shell) with a dangerous extension
4. The attacker uploads the malicious file, bypassing the inadequate file type restrictions
5. The attacker navigates to the uploaded file's URL to execute the malicious payload
6. The attacker gains remote code execution capabilities on the web server

For detailed technical information, refer to the Patchstack security advisory.

Detection Methods for CVE-2025-62016

Indicators of Compromise

• Unexpected PHP files or other executable scripts appearing in WordPress upload directories
• Newly created files in theme directories that were not part of legitimate updates
• Suspicious HTTP requests targeting unusual file paths within the KALLYAS theme structure
• Web server logs showing POST requests to upload endpoints followed by GET requests to unfamiliar PHP files

Detection Strategies

• Monitor file system changes in WordPress directories, particularly wp-content/uploads/ and theme folders, for newly created executable files
• Implement web application firewall (WAF) rules to detect and block upload attempts containing PHP code or other dangerous file types
• Review server access logs for patterns indicative of web shell deployment and subsequent command execution
• Conduct regular integrity checks comparing current files against known-good baselines of the WordPress installation

Monitoring Recommendations

• Enable detailed logging for all file upload activities within WordPress
• Configure alerting for creation of executable files in web-accessible directories
• Implement real-time file integrity monitoring on critical WordPress directories
• Monitor outbound network connections from the web server for unusual command-and-control traffic patterns

How to Mitigate CVE-2025-62016

Immediate Actions Required

• Update the KALLYAS WordPress theme to a patched version that addresses CVE-2025-62016 as soon as one becomes available from hogash
• Audit existing upload directories for any suspicious or unexpected files that may have been placed during an exploitation attempt
• Restrict file upload capabilities at the server level using .htaccess rules or web server configuration to deny execution of uploaded files
• Review WordPress user accounts and remove or demote any unnecessary accounts with upload privileges

Patch Information

Website administrators should check with hogash for an updated version of the KALLYAS theme that addresses this arbitrary file upload vulnerability. Monitor the Patchstack advisory for updates on patch availability. Until a patch is available, implement the workarounds described below to reduce exposure.

Workarounds

• Add .htaccess rules in upload directories to prevent PHP execution: php_flag engine off or equivalent Apache/Nginx configuration
• Implement a web application firewall (WAF) rule to block file uploads containing executable code patterns
• Consider temporarily disabling theme-specific upload functionality if not business-critical until a patch is released
• Restrict WordPress user registrations and audit existing user accounts to minimize authenticated attacker surface

# Example .htaccess configuration to prevent PHP execution in uploads directory
# Place this file in wp-content/uploads/

<FilesMatch "\.(?:php|phtml|php3|php4|php5|php7|phps)$">
    Order Deny,Allow
    Deny from all
</FilesMatch>

# Alternative for Apache 2.4+
<FilesMatch "\.(?:php|phtml|php3|php4|php5|php7|phps)$">
    Require all denied
</FilesMatch>