CVE-2018-16141 in ThinkCMF
Summary
by MITRE
ThinkCMF X2.2.3 has an arbitrary file deletion vulnerability in do_avatar in \application\User\Controller\ProfileController.class.php via an imgurl parameter with a ..\ sequence. A member user can delete any file on a Windows server.
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Analysis
by VulDB Data Team • 03/19/2020
The vulnerability identified as CVE-2018-16141 affects ThinkCMF version 2.2.3 and represents a critical arbitrary file deletion flaw within the application's user profile management functionality. This security weakness exists in the do_avatar method of the ProfileController.class.php file located in the application\User\Controller directory structure. The vulnerability specifically manifests through improper input validation of the imgurl parameter, which allows attackers to manipulate file paths using directory traversal sequences. The implementation fails to adequately sanitize user-supplied input, creating an opportunity for malicious actors to exploit the system's file handling mechanisms.
The technical exploitation of this vulnerability relies on the ability to inject ..\ sequences into the imgurl parameter, which enables attackers to traverse the file system directories beyond the intended scope of the application's avatar management functionality. On Windows servers, this vulnerability allows authenticated members with user privileges to delete arbitrary files from the server's file system, potentially compromising critical system files, application data, or user information. The flaw essentially bypasses normal file access controls by leveraging the directory traversal technique to navigate to restricted file locations and execute deletion operations against targeted files.
From an operational impact perspective, this vulnerability presents a severe threat to system integrity and data security within affected environments. An authenticated attacker with member-level privileges can leverage this weakness to remove critical application components, configuration files, or even system files that could lead to application instability, data loss, or complete system compromise. The vulnerability's impact extends beyond simple file deletion as it can be used to create persistent backdoors, remove security patches, or disable critical system functions. The attack vector requires minimal privileges but can result in significant damage to the application's availability and confidentiality.
Security professionals should recognize this vulnerability as a variant of CWE-22 - Improper Limitation of a Pathname to a Restricted Directory, which is categorized under the broader weakness of path traversal attacks. The vulnerability also aligns with ATT&CK technique T1059.007 - Command and Scripting Interpreter: Python, though in this case the exploitation occurs through web-based file system manipulation rather than direct command execution. The flaw demonstrates poor input validation practices and inadequate access control mechanisms that should be addressed through proper parameter sanitization, path restriction enforcement, and principle of least privilege implementation.
Mitigation strategies for this vulnerability should include immediate implementation of input validation measures that prevent directory traversal sequences from being processed within the imgurl parameter. Developers should enforce strict file path validation that rejects any input containing ..\ sequences or similar traversal patterns. Additionally, the application should implement proper access controls that limit file operations to predetermined directories and restrict file system access based on user privileges. The most effective remediation involves updating to a patched version of ThinkCMF or implementing custom input sanitization routines that validate and filter all user-supplied file paths before processing. Security monitoring should also be enhanced to detect unusual file deletion patterns that may indicate exploitation attempts. Organizations should conduct comprehensive security assessments to identify similar vulnerabilities within their application codebase and establish robust input validation frameworks to prevent future occurrences of this class of weakness.