CVE-2020-21554 in TinyShop
Summary
by MITRE • 03/25/2022
A File Deletion vulnerability exists in TinyShop 3.1.1 in the back_list parameter in controllers\admin.php, which could let a malicious user delete any file such as install.lock to reinstall cms.
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Analysis
by VulDB Data Team • 03/27/2022
The vulnerability identified as CVE-2020-21554 represents a critical file deletion flaw within TinyShop version 3.1.1 that exposes the content management system to unauthorized file manipulation. This vulnerability specifically affects the back_list parameter within the controllers/admin.php file, creating a path traversal and arbitrary file deletion attack vector that can be exploited by malicious actors to compromise the entire system. The flaw allows attackers to target critical system files including the install.lock file, which when deleted enables unauthorized reinstallation of the CMS, effectively undermining the security posture of the affected platform.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the administrative controller. When the back_list parameter is processed without proper authorization checks or file path validation, it creates an environment where malicious input can directly influence file system operations. This weakness aligns with CWE-22, which describes path traversal vulnerabilities, and CWE-77, which addresses command injection through improper input handling. The vulnerability operates at the application layer and can be exploited through HTTP requests that manipulate the back_list parameter to specify arbitrary file paths for deletion operations.
The operational impact of this vulnerability extends beyond simple file removal, as it provides attackers with a pathway to completely compromise the CMS installation. By deleting the install.lock file, attackers can gain unauthorized access to the installation process, potentially allowing them to reinstall the CMS with malicious configurations or inject backdoors. This vulnerability can be exploited by attackers with minimal privileges and can lead to complete system compromise, data loss, and potential lateral movement within network environments where the vulnerable system resides. The attack vector is particularly concerning as it requires no special privileges beyond basic access to the administrative interface and can be executed through standard web-based exploitation techniques.
Mitigation strategies for CVE-2020-21554 should focus on implementing robust input validation and access control measures within the application. The primary defense involves sanitizing all user-supplied input parameters, particularly those used in file system operations, and implementing proper authorization checks before executing any file manipulation commands. Organizations should also consider implementing the principle of least privilege for administrative functions and regularly audit file system permissions to prevent unauthorized deletion operations. The vulnerability can be addressed through patching the affected TinyShop version or implementing web application firewalls that can detect and block malicious parameter manipulation attempts. Additionally, security monitoring should be enhanced to detect unusual file deletion patterns that may indicate exploitation attempts, aligning with ATT&CK technique T1070.004 for Indicator Removal on Host. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other components of the system architecture, as this vulnerability demonstrates the importance of proper input validation in preventing critical file manipulation attacks.