CVE-2018-20127 in zzzphp
Summary
by MITRE
An issue was discovered in zzzphp cms 1.5.8. del_file in /admin/save.php allows remote attackers to delete arbitrary files via a mixed-case extension and an extra '.' character, because (for example) "php" is blocked but path=F:/1.phP. succeeds.
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Analysis
by VulDB Data Team • 04/20/2020
This vulnerability exists in zzzphp cms version 1.5.8 within the file deletion functionality implemented in the admin/save.php script. The flaw stems from inadequate input validation and sanitization mechanisms that fail to properly handle case-sensitive file extensions and malformed path specifications. Attackers can exploit this weakness by crafting malicious file paths that contain mixed-case extensions combined with extra period characters, effectively bypassing the security restrictions designed to prevent arbitrary file deletion. The vulnerability specifically targets the del_file function which processes file deletion requests through the administrative interface.
The technical implementation of this flaw demonstrates a classic path traversal and file manipulation vulnerability where the system performs insufficient validation of file paths before executing deletion operations. When an attacker submits a path such as F:/1.phP, the system incorrectly processes this input because it fails to normalize the case sensitivity of file extensions or properly validate the presence of multiple periods in the filename. This allows the system to interpret the malicious path as legitimate while bypassing the security checks that should prevent deletion of critical system files. The vulnerability essentially creates a condition where the file extension validation logic is circumvented through syntactic manipulation rather than content-based filtering.
The operational impact of this vulnerability is severe as it provides remote attackers with the ability to delete arbitrary files on the target system, potentially leading to complete system compromise. An attacker could leverage this weakness to remove critical application files, configuration files, or even system binaries that would render the cms inoperable. In a worst-case scenario, this vulnerability could enable attackers to delete database files, application source code, or administrative scripts, effectively disabling the content management system and potentially providing a foothold for further exploitation. The remote nature of this attack means that no local system access is required to exploit the vulnerability, making it particularly dangerous in publicly accessible environments.
Mitigation strategies for this vulnerability should focus on implementing robust input validation and sanitization measures that normalize file path specifications before processing. Organizations should ensure that all file operations include comprehensive validation that checks for case sensitivity variations, multiple periods, and other malformed path constructs that could be used to bypass security controls. The implementation should follow established security practices such as those outlined in the CWE-22 category for Path Traversal vulnerabilities and should incorporate proper file path normalization techniques. Additionally, access controls should be strengthened to limit administrative functions to authorized personnel only, and regular security audits should be conducted to identify similar vulnerabilities in other components of the application. The ATT&CK framework categorizes this as a privilege escalation technique through file system manipulation, emphasizing the need for defense in depth strategies including proper input validation and least privilege access controls.