CVE-2026-2665 Overview
A vulnerability has been identified in huanzi-qch base-admin, an open-source administrative framework. The vulnerability exists in the Upload function within the SysFileController.java file of the JSP Parser component. This flaw allows attackers to perform unrestricted file uploads by manipulating the File argument, potentially enabling remote code execution or other malicious activities on the target system.
Critical Impact
Unrestricted file upload vulnerabilities can allow attackers to upload malicious files including web shells, leading to complete system compromise through remote code execution.
Affected Products
- huanzi-qch base-admin (up to commit 57a8126bb3353a004f3c7722089e3b926ea83596)
- Systems running the affected base-admin JSP Parser component
- Deployments utilizing the SysFileController.java file upload functionality
Discovery Timeline
- 2026-02-18 - CVE-2026-2665 published to NVD
- 2026-02-19 - Last updated in NVD database
Technical Details for CVE-2026-2665
Vulnerability Analysis
This vulnerability is classified as an unrestricted file upload issue (CWE-284: Improper Access Control). The affected Upload function in SysFileController.java fails to properly validate or restrict the types of files that can be uploaded through the application. When processing file upload requests, the component does not adequately verify file extensions, MIME types, or file content, allowing attackers to upload arbitrary files to the server.
The vulnerability can be exploited remotely by authenticated users with access to the file upload functionality. Since the application uses continuous delivery with rolling releases, no specific version numbers are available to identify affected or patched releases.
Root Cause
The root cause of this vulnerability lies in improper access control and insufficient input validation within the file upload handling mechanism. The Upload function in SysFileController.java does not implement adequate checks to restrict which file types users can upload. This lack of file type validation allows attackers to bypass intended restrictions and upload potentially dangerous files such as JSP web shells or other executable content.
Attack Vector
The attack can be initiated remotely over the network by authenticated users. An attacker would need to:
- Authenticate to the base-admin application
- Access the file upload functionality exposed by SysFileController.java
- Craft a malicious file (such as a JSP web shell) with manipulated file metadata
- Upload the malicious file through the vulnerable Upload function
- Access the uploaded file to execute arbitrary code on the server
The vulnerability is publicly known and exploit details have been disclosed through the associated GitHub issue. The project maintainers were notified early through an issue report but have not yet responded.
Detection Methods for CVE-2026-2665
Indicators of Compromise
- Unexpected file uploads in web-accessible directories, particularly files with executable extensions (.jsp, .jspx, .war)
- Suspicious HTTP POST requests to the SysFileController upload endpoint with unusual file types
- Presence of web shell files or scripts in upload directories
- Unusual outbound network connections from the web server process
Detection Strategies
- Monitor file upload endpoints for suspicious file extensions or MIME type mismatches
- Implement file integrity monitoring on upload directories to detect unauthorized additions
- Review web server access logs for requests to newly uploaded files with executable extensions
- Deploy web application firewalls (WAF) with rules to block malicious file upload attempts
Monitoring Recommendations
- Enable detailed logging for all file upload operations in the base-admin application
- Configure alerts for file uploads with executable or suspicious extensions
- Implement periodic scans of upload directories for known web shell signatures
- Monitor system process trees for unexpected child processes spawned by the web application server
How to Mitigate CVE-2026-2665
Immediate Actions Required
- Review and restrict access to the file upload functionality in SysFileController.java
- Implement strict file type validation based on both extension and MIME type analysis
- Configure the upload directory to be non-executable and outside the web root
- Apply the principle of least privilege to users with file upload permissions
Patch Information
As of the last update on 2026-02-19, the project maintainers have not yet responded to the vulnerability disclosure reported through GitHub Issue #38. Since base-admin uses continuous delivery with rolling releases, users should monitor the project repository for updates addressing this issue. Additional technical details are available through VulDB #346462.
Workarounds
- Implement a whitelist of allowed file extensions at the application or web server level
- Configure file upload directories with non-executable permissions and restrict direct URL access
- Deploy a reverse proxy or WAF to filter malicious file upload requests before they reach the application
- Consider disabling the file upload functionality entirely if it is not critical to operations
# Example: Restrict upload directory permissions (Linux)
chmod 644 /path/to/upload/directory/*
chown www-data:www-data /path/to/upload/directory
# Disable script execution in upload directory (Apache)
# Add to .htaccess in upload directory:
# <Directory "/path/to/upload/directory">
# Options -ExecCGI
# RemoveHandler .jsp .jspx .war
# </Directory>
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
