CVE-2021-40639 in Jfinal
Summary
by MITRE • 09/16/2021
Improper access control in Jfinal CMS 5.1.0 allows attackers to access sensitive information via /classes/conf/db.properties&config=filemanager.config.js.
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Analysis
by VulDB Data Team • 07/05/2026
The vulnerability identified as CVE-2021-40639 represents a critical improper access control flaw within Jfinal CMS version 5.1.0 that exposes sensitive system configuration data to unauthorized actors. This weakness specifically manifests through the web application's handling of file access requests, where the application fails to properly validate user permissions when processing requests for configuration files. The vulnerability occurs at the application layer where the system does not adequately enforce authorization checks before serving sensitive files, creating an opportunity for attackers to bypass normal access controls and retrieve confidential information from the server.
The technical implementation of this flaw involves the application's improper handling of file path parameters in the URL structure, specifically when processing requests for database configuration files and file manager configurations. Attackers can exploit this by crafting malicious requests that target the /classes/conf/db.properties endpoint combined with the config=filemanager.config.js parameter, allowing them to access sensitive database connection strings, authentication credentials, and other critical system configuration data that should remain protected within the application's secure boundaries. This vulnerability directly maps to CWE-285, which addresses improper authorization issues in software systems, and demonstrates how weak access control mechanisms can lead to information disclosure.
The operational impact of this vulnerability extends beyond simple information disclosure, as the exposed database configuration files typically contain username and password credentials, database connection strings, and potentially encryption keys that could enable attackers to gain unauthorized access to backend databases. This access could lead to full system compromise, data exfiltration, and potential lateral movement within the network infrastructure. The vulnerability affects organizations using Jfinal CMS 5.1.0 who may not have proper network segmentation or additional security controls in place to protect against such direct file access attacks, making it particularly dangerous in environments where the application is exposed to untrusted networks.
Organizations should implement immediate mitigations including restricting direct access to configuration directories, implementing proper input validation and sanitization for all file path parameters, and deploying web application firewalls to detect and block suspicious requests targeting configuration files. The mitigation strategy should align with ATT&CK technique T1213.002, which focuses on data from information repositories, and emphasize the importance of proper access control enforcement. Additionally, regular security audits should verify that configuration files are stored outside of web-accessible directories and that proper authentication mechanisms are enforced before any sensitive file access is permitted. System administrators should also consider implementing automated monitoring for unusual file access patterns and ensure that all Jfinal CMS installations are updated to versions that address this specific access control vulnerability.