CVE-2021-36622 in Online Covid Vaccination Scheduler System
Summary
by MITRE • 08/03/2021
Sourcecodester Online Covid Vaccination Scheduler System 1.0 is affected vulnerable to Arbitrary File Upload. The admin panel has an upload function of profile photo accessible at http://localhost/scheduler/admin/?page=user. An attacker could upload a malicious file such as shell.php with the Content-Type: image/png. Then, the attacker have to visit the uploaded profile photo to access the shell.
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Analysis
by VulDB Data Team • 08/07/2021
The CVE-2021-36622 vulnerability affects the Sourcecodester Online Covid Vaccination Scheduler System version 1.0, representing a critical security flaw that enables unauthorized file upload capabilities within the administrative interface. This vulnerability stems from insufficient input validation and inadequate file type verification mechanisms within the profile photo upload functionality. The affected system exposes an administrative endpoint at http://localhost/scheduler/admin/?page=user where users can upload profile images without proper sanitization of file content or extension validation. The vulnerability specifically manifests when the application accepts files with the Content-Type header set to image/png while allowing execution of malicious code through file uploads, creating a pathway for attackers to bypass intended security controls. This flaw directly violates security principles by permitting arbitrary code execution through file upload mechanisms, which is a well-documented weakness in web application security frameworks.
The technical implementation of this vulnerability demonstrates a classic insecure file upload scenario where the application fails to validate file content against its declared MIME type or actual file characteristics. Attackers can exploit this by crafting a malicious file named shell.php but with a Content-Type header indicating it as an image/png file, thereby fooling the application's validation logic. The system's failure to verify actual file content against the declared type creates a condition where executable code can be silently uploaded and subsequently executed. This vulnerability aligns with CWE-434 which specifically addresses insecure file upload vulnerabilities, where applications accept files without proper validation of content, type, or security attributes. The flaw operates at the application layer and represents a significant bypass of security controls that should prevent execution of code within user-uploaded content.
The operational impact of this vulnerability is severe as it provides attackers with complete command execution capabilities within the application's environment, potentially enabling full system compromise. Once an attacker successfully uploads a malicious file, they can execute arbitrary commands on the server, potentially gaining access to sensitive vaccination data, user information, and other critical system resources. The vulnerability creates a persistent backdoor that can be exploited repeatedly, allowing attackers to maintain access and escalate privileges over time. This represents a critical threat to the confidentiality, integrity, and availability of the vaccination scheduling system, particularly concerning healthcare data protection requirements and regulatory compliance. The attack vector is straightforward and requires minimal technical expertise, making it particularly dangerous for systems handling sensitive medical information.
Mitigation strategies for CVE-2021-36622 should focus on implementing comprehensive file validation mechanisms that verify both file content and type through multiple verification methods. The system must implement strict file type checking using content-based validation rather than relying solely on MIME headers or file extensions. Security controls should include server-side validation that examines actual file signatures, implements whitelisting of allowed file types, and enforces proper file naming conventions. Additionally, uploaded files should be stored in non-executable directories and renamed to prevent direct access to uploaded content. The implementation should follow ATT&CK framework techniques for defensive measures against file upload attacks, specifically focusing on preventing execution of uploaded files and implementing proper access controls. Organizations should also implement network segmentation, regular security assessments, and monitoring of upload activities to detect and prevent exploitation attempts. The vulnerability highlights the critical need for defense-in-depth strategies that combine multiple security controls to protect against similar attack vectors and ensure compliance with healthcare data protection standards.