CVE-2018-19181 in YUNUCMS
Summary
by MITRE
statics/ueditor/php/vendor/Local.class.php in YUNUCMS 1.1.5 allows arbitrary file deletion via the statics/ueditor/php/controller.php?action=remove key parameter, as demonstrated by using directory traversal to delete the install.lock file.
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Analysis
by VulDB Data Team • 04/11/2020
The vulnerability identified as CVE-2018-19181 resides within the YUNUCMS content management system version 1.1.5, specifically in the file statics/ueditor/php/vendor/Local.class.php. This flaw represents a critical authorization and access control issue that enables attackers to perform arbitrary file deletion operations through improper input validation mechanisms. The vulnerability manifests when the system processes the remove action parameter within the controller.php file, allowing malicious actors to manipulate the directory traversal functionality to target and delete critical system files including the install.lock file that typically prevents unauthorized reinstallation of the CMS.
The technical exploitation of this vulnerability stems from insufficient validation of user-supplied input parameters within the file deletion functionality. When the action parameter is set to remove, the system fails to properly sanitize or validate the key parameter that specifies which file should be deleted. This lack of input validation creates a path traversal condition where attackers can manipulate the file path to target files outside the intended directory scope. The vulnerability directly maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as directory traversal or path traversal attacks. The flaw allows attackers to bypass normal file access controls and delete files that should remain protected, potentially compromising the entire system integrity.
The operational impact of this vulnerability is severe and multifaceted, as it provides attackers with the capability to compromise the CMS installation at multiple levels. By deleting the install.lock file, attackers can potentially reinitialize the CMS installation process, gaining unauthorized access to administrative functions and potentially leading to full system compromise. The vulnerability also creates opportunities for attackers to delete critical system files, configuration files, or log files that could disrupt service availability or hide malicious activities. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1070.004, which involves the deletion or modification of existing system binaries and files, potentially enabling further persistence or evasion tactics.
Mitigation strategies for this vulnerability should focus on implementing robust input validation and access control measures. The primary recommendation involves sanitizing all user-supplied parameters before processing them within the file deletion functionality, specifically ensuring that the key parameter cannot contain directory traversal sequences such as ../ or ..\. Additionally, implementing proper authorization checks that verify the user's permissions before executing any file deletion operations is essential. The system should also enforce strict file path validation to ensure that all file operations occur within predetermined safe directories. Organizations should also consider implementing principle of least privilege access controls for the CMS file system, limiting write permissions to only necessary administrative accounts and implementing proper logging mechanisms to detect unauthorized file deletion attempts. Regular security audits and input validation testing should be conducted to prevent similar vulnerabilities from being introduced in future code releases, while also ensuring that existing installations are updated to patched versions that address this specific directory traversal flaw.