CVE-2026-24673: Open eClass Path Traversal Vulnerability

CVE-2026-24673 Overview

CVE-2026-24673 is a file upload validation bypass vulnerability affecting the Open eClass platform (formerly known as GUnet eClass), a complete course management system used by educational institutions. Prior to version 4.2, attackers can bypass file upload restrictions by embedding files with prohibited extensions inside ZIP archives. When these archives are extracted using the application's built-in decompression functionality, the malicious files are written to the server without proper validation.

This vulnerability is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type), which represents a common attack vector for web applications that fail to properly validate uploaded content during multi-step processing workflows.

Critical Impact

Successful exploitation could allow authenticated attackers to upload malicious files such as web shells or executable scripts to the server, potentially leading to remote code execution, data theft, or complete system compromise of the e-learning platform.

Affected Products

• Open eClass platform versions prior to 4.2
• GUnet eClass (legacy naming) versions prior to 4.2

Discovery Timeline

• 2026-02-03 - CVE CVE-2026-24673 published to NVD
• 2026-02-04 - Last updated in NVD database

Technical Details for CVE-2026-24673

Vulnerability Analysis

The vulnerability resides in the file upload handling mechanism within Open eClass, specifically in how the platform processes ZIP archive uploads and subsequent extraction operations. While the application implements file extension validation during the initial upload phase, this validation is not consistently applied when files are extracted from ZIP archives.

The exploitation workflow involves an authenticated attacker uploading a specially crafted ZIP archive containing files with restricted extensions (such as .php, .phtml, .cgi, or other executable file types). During the extraction process, the decompression functionality writes these embedded files to the server's file system without re-validating their extensions against the allowed file type list.

This represents a classic validation bypass pattern where security controls applied at one processing stage are circumvented by leveraging a secondary processing mechanism that lacks equivalent protections.

Root Cause

The root cause stems from inconsistent input validation between the primary file upload handler and the ZIP extraction functionality. The application's security model assumes that files extracted from archives have already been validated, creating a trust boundary violation. The decompression routine lacks independent file type verification, allowing malicious payloads to bypass the initial upload restrictions.

Attack Vector

The attack requires network access and authenticated user privileges within the Open eClass platform. An attacker with valid credentials (such as a student or instructor account) can exploit this vulnerability through the following general approach:

1. Create a ZIP archive containing a malicious file with a prohibited extension (e.g., a PHP web shell)
2. Upload the ZIP archive through the platform's file upload functionality, where the .zip extension passes validation
3. Trigger the built-in extraction feature to decompress the archive contents
4. The malicious file is extracted and written to the server without extension validation
5. Access the extracted malicious file directly to execute arbitrary code or commands

The attack does not require user interaction beyond the initial authentication and can be performed by any user with upload permissions. For technical implementation details, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-24673

Indicators of Compromise

• Unexpected executable files (.php, .phtml, .cgi, .asp, .aspx, .jsp) appearing in upload directories
• Web server access logs showing requests to unusual file paths within the Open eClass upload structure
• ZIP archives uploaded by users followed by HTTP requests to newly created files with executable extensions
• Anomalous file creation events in the web application's upload directories

Detection Strategies

• Implement file integrity monitoring on Open eClass upload directories to detect unauthorized file creation
• Monitor web server logs for POST requests to upload endpoints followed by GET requests to suspicious file paths
• Deploy web application firewall (WAF) rules to inspect ZIP archive contents before processing
• Review authentication logs for accounts uploading unusually large numbers of ZIP files

Monitoring Recommendations

• Configure alerts for file creation events in web-accessible directories with executable extensions
• Implement application-level logging to track ZIP extraction operations and resulting file paths
• Establish baseline upload patterns for users and alert on deviations indicative of exploitation attempts

How to Mitigate CVE-2026-24673

Immediate Actions Required

• Upgrade Open eClass platform to version 4.2 or later immediately
• Review upload directories for any suspicious files with executable extensions that may indicate prior exploitation
• Temporarily disable ZIP archive upload and extraction functionality if immediate patching is not possible
• Audit user accounts with upload permissions for any signs of compromise

Patch Information

The vulnerability has been addressed in Open eClass version 4.2. Organizations running earlier versions should update immediately. The patch implements consistent file extension validation during the ZIP extraction process, ensuring that files with prohibited extensions cannot be written to the server regardless of the upload method.

For detailed patch information and upgrade instructions, consult the GitHub Security Advisory.

Workarounds

• Disable ZIP file upload functionality at the web server level until the patch can be applied
• Implement a web application firewall rule to block ZIP file uploads to the affected application
• Configure file system permissions to prevent the web server process from creating files with executable extensions in upload directories
• Use server-side scanning to inspect extracted archive contents before making them accessible

# Example: Apache configuration to block executable files in upload directory
<Directory "/var/www/openeclass/uploads">
    # Deny execution of scripts in upload directory
    <FilesMatch "\.(php|phtml|cgi|pl|py|asp|aspx|jsp)$">
        Require all denied
    </FilesMatch>
</Directory>