CVE-2011-5161 in OpenEMR
Summary
by MITRE
Unrestricted file upload vulnerability in the patient photograph functionality in OpenEMR 4 allows remote attackers to execute arbitrary PHP code by uploading a file with an executable extension followed by a safe extension, then accessing it via a direct request to the patient directory under documents/.
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Analysis
by VulDB Data Team • 12/29/2024
The vulnerability identified as CVE-2011-5161 represents a critical unrestricted file upload flaw within the patient photograph functionality of OpenEMR version 4. This security weakness stems from inadequate input validation and file extension filtering mechanisms that permit malicious actors to bypass upload restrictions through a sophisticated technique involving dual file extensions. The vulnerability exists within a healthcare information system that processes sensitive patient data, making it particularly dangerous given the regulatory requirements and data protection standards governing medical information. The flaw allows remote attackers to execute arbitrary PHP code, which constitutes a severe privilege escalation risk that could lead to complete system compromise and unauthorized access to protected health information.
The technical implementation of this vulnerability exploits a specific file extension handling mechanism where attackers can upload files with executable extensions such as .php followed by legitimate extensions like .jpg or .png. This technique exploits the way the application processes file uploads and determines file types, often through basic string matching or regex patterns that fail to account for the presence of multiple extensions. The application's file validation logic appears to only examine the final portion of the filename extension rather than performing comprehensive file type verification, creating a window of opportunity for attackers to inject malicious code. This type of vulnerability is classified under CWE-434 Unrestricted Upload of File with Dangerous Type, which specifically addresses scenarios where applications allow file uploads without proper validation of file content or type. The attack vector specifically targets the patient directory under the documents/ path, indicating that the vulnerability exists in the document management subsystem where patient photographs are stored.
The operational impact of this vulnerability extends far beyond simple code execution, as it provides attackers with persistent access to a healthcare system containing sensitive patient information. Once an attacker successfully uploads malicious code, they can execute arbitrary commands on the server, potentially leading to data exfiltration, system compromise, or deployment of additional malware. The direct request access pattern suggests that attackers can immediately execute their payloads without requiring additional exploitation steps, making this vulnerability particularly dangerous. The implications are severe given that OpenEMR systems typically handle Protected Health Information (PHI) subject to HIPAA regulations, meaning that any successful exploitation could result in significant compliance violations and potential legal consequences. The vulnerability also aligns with ATT&CK technique T1190 Exploit Public-Facing Application, which describes methods used by adversaries to exploit vulnerabilities in externally accessible applications.
Organizations utilizing OpenEMR version 4 should implement immediate mitigations including comprehensive input validation, strict file type verification, and removal of executable extensions from upload allowances. The system should employ content-based file type detection rather than relying solely on extension checks, implementing proper MIME type validation and file signature verification. Additionally, uploaded files should be stored in non-executable directories, and proper access controls should be enforced to prevent direct execution of uploaded content. The fix should also include implementing a whitelist approach for allowed file extensions and ensuring that uploaded files are processed through a secure sandbox environment before being made available to users. Organizations should also consider implementing web application firewalls and monitoring for suspicious upload patterns to detect potential exploitation attempts. These measures align with security best practices outlined in NIST SP 800-53 and ISO 27001 standards for protecting sensitive information systems and maintaining regulatory compliance in healthcare environments.