CVE-2018-17797 in zzcms
Summary
by MITRE
An issue was discovered in zzcms 8.3. user/zssave.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 • 03/28/2020
The vulnerability identified as CVE-2018-17797 affects zzcms version 8.3 and represents a critical directory traversal flaw in the user/zssave.php component. This security weakness enables remote attackers to manipulate file operations by injecting directory traversal sequences into the oldimg parameter during modify actions. The flaw stems from inadequate input validation and sanitization mechanisms that fail to properly filter user-supplied data before processing file operations. The vulnerability specifically manifests when the application processes requests with action=modify and the oldimg parameter containing malicious traversal sequences such as ../ or ..\ which allow attackers to navigate outside the intended directory boundaries. This directory traversal capability fundamentally undermines the application's file access controls and creates an avenue for arbitrary file deletion operations.
The operational impact of this vulnerability extends beyond simple file deletion to encompass potential database access and system compromise. When attackers successfully exploit the directory traversal flaw to delete the install.lock file, they gain unauthorized access to the database management system and can potentially execute further malicious activities. The install.lock file typically serves as a protection mechanism that prevents unauthorized database modifications during the installation process, and its deletion removes critical access controls that protect the underlying database infrastructure. This creates a cascading security risk where the initial directory traversal attack can lead to full database compromise, data exfiltration, and potential system takeover. The vulnerability operates under the CWE-22 category for Improper Limitation of a Pathname to a Restricted Directory, which is classified as a path traversal attack pattern.
Security practitioners should note that this vulnerability aligns with several ATT&CK tactics including TA0006 Privilege Escalation and TA0005 Defense Evasion. The attack chain begins with initial access through the directory traversal vector and progresses toward privilege escalation by removing installation locks that protect database integrity. Defense evasion occurs as the attacker can manipulate file systems to hide malicious activities or establish persistence mechanisms. The vulnerability demonstrates how seemingly simple input validation failures can create severe security implications, particularly in content management systems where file operations are frequently performed. Organizations should implement proper input sanitization, establish strict file access controls, and employ web application firewalls to detect and prevent directory traversal attempts. Additionally, regular security audits and code reviews should focus on file operation handling to identify similar vulnerabilities in other components. The exploitability of this vulnerability highlights the importance of secure coding practices and the necessity of implementing robust access control mechanisms that prevent unauthorized file system modifications regardless of the user's privileges.