CVE-2024-38909: Std42 Elfinder Auth Bypass Vulnerability

CVE-2024-38909 Overview

CVE-2024-38909 is an Incorrect Access Control vulnerability affecting Studio 42 elFinder version 2.1.64. This file manager application, commonly used in web applications to provide file browsing and management capabilities, contains a flaw that allows attackers to copy files with unauthorized extensions between server directories. Successful exploitation can lead to exposure of sensitive information and remote code execution (RCE).

Critical Impact

This vulnerability enables unauthenticated attackers to bypass file extension restrictions, potentially uploading malicious files to execute arbitrary code on vulnerable servers or exfiltrate sensitive data.

Affected Products

• Studio 42 elFinder version 2.1.64
• Web applications integrating elFinder 2.1.64 as their file manager component
• Content Management Systems (CMS) using the vulnerable elFinder library

Discovery Timeline

• 2024-07-30 - CVE-2024-38909 published to NVD
• 2025-04-28 - Last updated in NVD database

Technical Details for CVE-2024-38909

Vulnerability Analysis

The vulnerability resides in elFinder's file handling mechanisms, specifically in how the application validates and enforces file extension restrictions during copy operations between directories. The access control implementation fails to properly verify whether a user has authorization to manipulate files with certain extensions when performing inter-directory copy operations.

This Broken Access Control flaw (CWE-284) allows an attacker to circumvent security restrictions that would normally prevent the handling of potentially dangerous file types. The network-accessible nature of this vulnerability means remote attackers can exploit it without requiring any authentication or user interaction, making it particularly dangerous for internet-facing deployments.

Root Cause

The root cause of this vulnerability stems from insufficient access control validation in the file copy functionality. When files are copied between server directories, the application fails to enforce the same extension restrictions that apply during file upload operations. This inconsistency in security enforcement creates a bypass vector where attackers can manipulate files with restricted extensions (such as .php, .phtml, or other executable types) by first uploading them with an allowed extension and then copying them with a malicious extension, or by exploiting existing files on the system.

Attack Vector

The attack vector is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by:

1. Identifying a web application running the vulnerable elFinder 2.1.64 component
2. Accessing the elFinder interface (often exposed at predictable paths)
3. Utilizing the copy functionality to transfer files between directories while bypassing extension restrictions
4. Exploiting the copied files to achieve remote code execution or access sensitive configuration files

The vulnerability can be exploited through crafted HTTP requests to the elFinder connector endpoint, manipulating the copy operation parameters to bypass file type restrictions.

For detailed technical exploitation information, refer to the GitHub CVE-2024-38909 Details documentation.

Detection Methods for CVE-2024-38909

Indicators of Compromise

• Unusual file copy operations in elFinder logs, particularly involving executable extensions (.php, .phtml, .asp, .jsp)
• Presence of unexpected script files in web-accessible directories
• HTTP requests to elFinder connector endpoints with suspicious cmd=copy operations
• New or modified files with mismatched creation and modification timestamps in upload directories

Detection Strategies

• Monitor web server logs for requests to elFinder connector endpoints containing copy commands with executable file extensions
• Implement file integrity monitoring (FIM) on directories managed by elFinder to detect unauthorized file additions
• Configure Web Application Firewall (WAF) rules to alert on suspicious elFinder API requests
• Review access logs for unauthenticated or anomalous access patterns to file management interfaces

Monitoring Recommendations

• Enable detailed logging for all elFinder operations, including file copy, move, and rename actions
• Implement real-time alerting for the creation of executable files in upload directories
• Deploy endpoint detection and response (EDR) solutions to monitor for web shell activity
• Establish baseline behavior for elFinder usage and alert on deviations

How to Mitigate CVE-2024-38909

Immediate Actions Required

• Audit all web applications for the presence of elFinder version 2.1.64 and restrict access to the file manager interface
• Implement network-level access controls to limit who can reach elFinder endpoints
• Review and remove any unauthorized or suspicious files from directories managed by elFinder
• Consider temporarily disabling elFinder functionality until a patched version is deployed

Patch Information

Organizations should monitor the elFinder Official Website and the project's GitHub repository for security updates addressing this vulnerability. Upgrade to a patched version of elFinder as soon as one becomes available. In the meantime, implement the recommended workarounds to reduce exposure.

Workarounds

• Restrict access to elFinder interfaces using authentication and IP-based access controls
• Configure the web server to prevent execution of scripts in elFinder upload/storage directories using directory-specific configurations
• Implement strict Content Security Policy (CSP) headers to mitigate potential exploitation
• Disable the copy functionality in elFinder configuration if not required for business operations

# Apache configuration to prevent script execution in upload directories
<Directory "/var/www/html/files/elfinder/uploads">
    # Disable PHP execution
    php_admin_flag engine off
    
    # Deny access to script files
    <FilesMatch "\.(php|phtml|php3|php4|php5|pl|cgi|py|asp|aspx|jsp)$">
        Require all denied
    </FilesMatch>
    
    # Set restrictive handler
    RemoveHandler .php .phtml .php3 .php4 .php5
    AddHandler txt .php .phtml .php3 .php4 .php5
</Directory>