CVE-2020-8639 in TestLink
Summary
by MITRE
An unrestricted file upload vulnerability in keywordsImport.php in TestLink 1.9.20 allows remote attackers to execute arbitrary code by uploading a file with an executable extension. This allows an authenticated attacker to upload a malicious file (containing PHP code to execute operating system commands) to a publicly accessible directory of the application.
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Analysis
by VulDB Data Team • 02/09/2025
The vulnerability identified in TestLink 1.9.20 represents a critical unrestricted file upload flaw that enables remote code execution through the keywordsImport.php component. This issue stems from inadequate input validation and sanitization mechanisms within the application's file handling process, allowing authenticated users to bypass security restrictions and upload malicious files with executable extensions. The vulnerability occurs when the application fails to properly validate file types or extensions during the upload process, creating an attack vector that can be exploited by threat actors with valid credentials.
The technical implementation of this flaw involves the application's failure to enforce strict file type validation checks before storing uploaded files in publicly accessible directories. When an authenticated attacker uploads a file containing php code, the system processes the request without proper extension filtering or content verification, resulting in the storage of executable payloads within directories that are accessible via web requests. This allows the malicious code to be executed directly by the web server when accessed through standard http requests, providing attackers with arbitrary command execution capabilities on the underlying operating system.
From an operational perspective, this vulnerability presents a severe risk to TestLink installations as it enables authenticated attackers to escalate privileges and gain full control over the application server. The impact extends beyond simple code execution, potentially allowing attackers to establish persistent backdoors, exfiltrate sensitive data, or use the compromised system as a launch point for further attacks within the network infrastructure. The vulnerability's exploitation requires only valid authentication credentials, making it particularly dangerous in environments where user access controls are insufficient or where credentials may be compromised through phishing or other social engineering techniques.
The security implications of this vulnerability align with CWE-434 which specifically addresses unrestricted Upload of executable code, and can be mapped to ATT&CK technique T1190 for exploiting vulnerabilities in web applications. Organizations should implement immediate mitigations including strict file type validation, mandatory extension filtering, content-based file verification, and proper access controls for upload directories. Additionally, the application should enforce directory permissions that prevent execution of uploaded files in web-accessible locations while implementing comprehensive logging and monitoring for suspicious file upload activities. Regular security assessments and vulnerability scanning should be conducted to identify similar issues across other components within the TestLink application or related systems that may present similar attack vectors.