CVE-2018-8969 in zzcms
Summary
by MITRE
An issue was discovered in zzcms 8.2. user/licence_save.php allows remote attackers to delete arbitrary files via directory traversal sequences in the oldimg parameter in an action=modify request. This can be leveraged for database access by deleting install.lock.
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Analysis
by VulDB Data Team • 01/16/2020
The vulnerability identified as CVE-2018-8969 resides within zzcms version 8.2, specifically in the user/licence_save.php file where improper input validation allows remote attackers to execute arbitrary file deletion operations through directory traversal sequences. This flaw manifests when the oldimg parameter is manipulated within an action=modify request, enabling attackers to navigate outside the intended directory structure and target files for deletion. The vulnerability represents a critical security weakness that directly violates the principle of least privilege and proper input sanitization.
The technical implementation of this vulnerability stems from inadequate validation of user-supplied input parameters, particularly the oldimg parameter which should have been restricted to specific directories or validated against a whitelist of acceptable file paths. Attackers can exploit this by crafting malicious directory traversal sequences such as ../../../ or similar patterns that allow them to traverse the file system beyond the intended boundaries. This weakness aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal vulnerabilities.
The operational impact of this vulnerability is severe and multifaceted, as it provides attackers with the capability to delete critical system files including the install.lock file that typically prevents unauthorized database access during installation or upgrade processes. When the install.lock file is removed, it can potentially allow attackers to gain unauthorized access to the database or perform unauthorized modifications to the application's configuration and data. This creates a chain of compromise that can lead to complete system takeover or data exfiltration, making it particularly dangerous for web applications that handle sensitive user information or business-critical data.
The attack vector for this vulnerability is accessible via remote exploitation without requiring authentication, making it particularly dangerous as it can be leveraged by anyone with access to the web application. The vulnerability demonstrates a fundamental flaw in the application's security architecture where input validation occurs too late in the processing chain, allowing malicious input to reach the file system operations. Security practitioners should note that this vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as the exploitation may involve manipulation of file system operations through web-based interfaces.
Mitigation strategies should include immediate implementation of proper input validation and sanitization for all user-supplied parameters, particularly those used in file system operations. The application should enforce strict path validation that prevents directory traversal sequences and restricts file operations to predefined safe directories. Additionally, implementing a whitelist approach for acceptable file paths and ensuring that file system operations are performed with minimal required privileges can significantly reduce the impact of such vulnerabilities. Regular security audits and input validation testing should be conducted to identify and remediate similar weaknesses in the application's codebase. Organizations should also consider implementing web application firewalls and intrusion detection systems to monitor for exploitation attempts of this type of vulnerability, while ensuring that all software components are kept up to date with the latest security patches and updates.