CVE-2018-20063 in TestRail
Summary
by MITRE
An issue was discovered in Gurock TestRail 5.6.0.3853. An "Unrestricted Upload of File" vulnerability exists in the image-upload form (available in the description editor), allowing remote authenticated users to execute arbitrary code by uploading an image file with an executable extension but a safe Content-Type value, and then accessing it via a direct request to the file in the file-upload directory (if it's accessible according to the server configuration).
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Analysis
by VulDB Data Team • 07/19/2023
The vulnerability identified as CVE-2018-20063 represents a critical security flaw in Gurock TestRail version 5.6.0.3853 that stems from inadequate file validation mechanisms within the image upload functionality. This issue manifests in the description editor component where users can upload images to enhance test case descriptions, creating a pathway for malicious actors to bypass security controls through clever manipulation of file attributes. The vulnerability specifically exploits the system's reliance on Content-Type headers rather than comprehensive file extension validation, allowing attackers to execute code through seemingly benign image uploads.
The technical implementation of this vulnerability involves a classic unrestricted file upload scenario where the application accepts files based primarily on their reported Content-Type rather than conducting thorough file type verification. Attackers can exploit this by crafting image files with executable extensions such as .php, .asp, or .jsp while maintaining legitimate image Content-Type headers like image/jpeg or image/png. This technique leverages the principle that many web servers and applications perform file validation checks based on HTTP headers rather than actual file content analysis, creating a window of opportunity for code execution.
The operational impact of this vulnerability extends beyond simple code execution to encompass full system compromise potential, as authenticated users with upload privileges can leverage this flaw to gain unauthorized access to the underlying server infrastructure. The vulnerability's exploitation requires only a direct request to the uploaded file location, making it particularly dangerous in environments where file upload directories are accessible via standard web requests. This creates a persistent threat vector that can be exploited repeatedly until the underlying validation mechanisms are properly addressed, potentially allowing attackers to establish backdoors, exfiltrate data, or perform further reconnaissance activities.
From a cybersecurity framework perspective, this vulnerability maps directly to CWE-434 Unrestricted Upload of File with Dangerous Type, which is categorized under the OWASP Top Ten 2017 as A04:2017 - Insecure Design and represents a fundamental flaw in input validation controls. The ATT&CK framework classification would place this under T1059.007 Command and Scripting Interpreter: JavaScript, as the malicious code execution could involve scripting languages, and potentially T1078 Valid Accounts for the requirement of authenticated access to exploit the vulnerability. The vulnerability demonstrates poor defense-in-depth principles where multiple layers of security controls should have been implemented to prevent such bypass scenarios.
Effective mitigation strategies must address both the immediate technical flaw and implement comprehensive security controls to prevent similar issues. Organizations should implement strict file validation mechanisms that check both file extensions and actual file content rather than relying solely on Content-Type headers. The solution requires enforcing a whitelist approach for acceptable file types, implementing proper file name sanitization, and ensuring that uploaded files are stored outside the web root directory or are properly protected through server configuration. Additionally, implementing Content Security Policy headers, regular security audits of file upload functionalities, and maintaining up-to-date application versions through proper patch management procedures are essential measures to prevent exploitation of such vulnerabilities. The remediation should also include monitoring for suspicious file upload activities and implementing proper access controls to limit who can perform file uploads within the application.