CVE-2018-13038 in OpenSID
Summary
by MITRE
OpenSID 18.06-pasca has an Unrestricted File Upload vulnerability via an Attachment Document in the article feature. This vulnerability leads to uploading arbitrary PHP code via a .php filename with the application/pdf Content-Type.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 03/29/2023
The vulnerability identified as CVE-2018-13038 affects OpenSID version 18.06-pasca and represents a critical security flaw in the article feature's attachment handling mechanism. This issue stems from insufficient input validation and sanitization processes that fail to properly verify file types and content before allowing uploads to the server. The vulnerability specifically manifests when users attempt to upload documents through the article functionality, creating a pathway for malicious actors to bypass normal security controls and execute arbitrary code on the target system.
The technical exploitation of this vulnerability occurs through a sophisticated bypass technique that leverages the application's permissive file validation logic. Attackers can craft malicious files with .php extensions while disguising their content type as application/pdf, effectively circumventing the expected file type restrictions. This approach exploits the server's reliance on Content-Type headers for validation rather than implementing comprehensive file signature checking or extension-based filtering. The flaw resides in the application's file upload validation routines which do not perform thorough content analysis or enforce strict file type constraints, allowing PHP code execution payloads to be silently accepted and stored on the server.
The operational impact of this vulnerability extends beyond simple code execution, creating a comprehensive attack surface that enables remote code execution and potential system compromise. Once successfully exploited, attackers can upload malicious PHP scripts that execute with the privileges of the web server process, potentially leading to full system compromise, data exfiltration, or the establishment of persistent backdoors. The vulnerability is particularly dangerous because it operates silently without requiring authentication, making it accessible to any user with access to the article attachment feature. This flaw directly aligns with CWE-434, which addresses unrestricted upload of files with dangerous types, and represents a classic example of insecure file upload handling that can be exploited for privilege escalation and persistent access.
Mitigation strategies for CVE-2018-13038 must address both immediate defensive measures and long-term architectural improvements to prevent similar vulnerabilities. Organizations should implement comprehensive file validation that checks not only file extensions but also file signatures, content type headers, and actual file content to ensure uploaded files match their declared types. The solution requires enforcing strict file type restrictions, implementing proper file naming conventions, and ensuring uploaded files are stored outside the web root directory. Additionally, the application should employ multiple validation layers including server-side checks, content type verification, and file format analysis to prevent attackers from exploiting the vulnerability through Content-Type header manipulation. Organizations should also consider implementing the principle of least privilege for web server processes and deploy web application firewalls to detect and block suspicious upload attempts. The remediation process must include comprehensive testing to ensure that file upload functionality properly rejects malicious files while maintaining legitimate functionality for authorized users. This vulnerability demonstrates the critical importance of defense-in-depth strategies and proper input validation as outlined in the ATT&CK framework's technique for file and directory permissions modification, where attackers exploit weak file handling to establish persistent access to systems.