CVE-2019-8933 in DeDeCMS
Summary
by MITRE
In DedeCMS 5.7SP2, attackers can upload a .php file to the uploads/ directory (without being blocked by the Web Application Firewall), and then execute this file, via this sequence of steps: visiting the management page, clicking on the template, clicking on Default Template Management, clicking on New Template, and modifying the filename from ../index.html to ../index.php.
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Analysis
by VulDB Data Team • 07/11/2023
The vulnerability identified as CVE-2019-8933 represents a critical file upload flaw in DedeCMS version 5.7SP2 that directly enables remote code execution capabilities for attackers. This vulnerability stems from insufficient input validation and access control mechanisms within the content management system's template management functionality. The flaw allows unauthorized users to bypass security restrictions that should prevent the upload of executable files to the web server's upload directory. The vulnerability specifically manifests when users navigate through the administrative interface to the template management section, where the system fails to properly validate file extensions or implement proper access controls for file operations.
The technical exploitation of this vulnerability follows a well-defined attack pattern that leverages the CMS's template management interface. Attackers begin by accessing the management page and navigate through the template section to reach the default template management functionality. The vulnerability becomes apparent when users can modify template filenames from standard HTML extensions to PHP extensions, effectively creating a backdoor file that can be executed on the web server. This particular flaw is classified under CWE-434 which specifically addresses "Unrestricted Upload of File with Dangerous Type," indicating that the system fails to properly validate file types and restricts the upload of potentially malicious files. The vulnerability also aligns with CWE-22 which covers "Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')", as the attack involves manipulating file paths to place malicious code in the upload directory.
The operational impact of CVE-2019-8933 is severe and far-reaching, as it provides attackers with a direct pathway to achieve persistent remote code execution on affected systems. Once a malicious PHP file is successfully uploaded, attackers can execute arbitrary code with the privileges of the web server process, potentially leading to complete system compromise. This vulnerability enables attackers to establish backdoors, exfiltrate sensitive data, deploy additional malware, or use the compromised system as a launch point for further attacks within the network. The impact extends beyond immediate system compromise to include potential data breaches, service disruption, and regulatory compliance violations. The vulnerability's exploitation does not require authentication for the upload process, making it particularly dangerous as it can be exploited by anyone with access to the CMS management interface or through other attack vectors that lead to administrative access.
Mitigation strategies for CVE-2019-8933 must address both immediate remediation and long-term security enhancements. The primary recommendation involves applying the official security patch released by DedeCMS developers to address the template upload validation flaw. Organizations should also implement additional security controls including strict file type validation, mandatory file extension filtering, and proper access controls for upload directories. Network segmentation and web application firewalls should be configured to monitor and restrict file upload operations to specific directories. Security configurations should enforce proper file permissions that prevent execution of uploaded files in web-accessible directories, and implement proper input sanitization for all user-supplied data. The remediation process should also include comprehensive security audits of all CMS components and regular vulnerability assessments to identify similar flaws. This vulnerability demonstrates the importance of following secure coding practices and implementing defense-in-depth strategies as outlined in the MITRE ATT&CK framework under the T1190 technique for "Exploit Public-Facing Application" and T1059 for "Command and Scripting Interpreter" which are directly applicable to this type of vulnerability exploitation.