CVE-2021-3256 in KuaiFanCMS
Summary
by MITRE • 06/12/2021
KuaiFanCMS V5.x contains an arbitrary file read vulnerability in the html_url parameter of the chakanhtml.module.php file.
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Analysis
by VulDB Data Team • 06/14/2021
The KuaiFanCMS V5.x arbitrary file read vulnerability represents a critical security flaw that allows attackers to access sensitive files on the affected system through improper input validation. This vulnerability exists within the chakanhtml.module.php file where the html_url parameter is processed without adequate sanitization or authorization checks. The flaw enables unauthorized users to read arbitrary files from the server filesystem, potentially exposing configuration files, database credentials, application source code, and other sensitive information. Such vulnerabilities are particularly dangerous in content management systems as they often provide access to the underlying server infrastructure and can serve as a foothold for further exploitation. The vulnerability falls under the category of insecure direct object references as described in CWE-22, where user-supplied input directly references files without proper validation. This type of vulnerability is commonly exploited in the initial reconnaissance phase of cyber attacks and can lead to complete system compromise when combined with other exploitation techniques.
The technical implementation of this vulnerability stems from the lack of proper input validation and access control mechanisms within the chakanhtml.module.php file. When the html_url parameter is processed, the application fails to verify whether the requested file path is within the intended directory scope or if the user has proper authorization to access the specified resource. Attackers can leverage this weakness by crafting malicious requests that include directory traversal sequences such as ../ or ..\ to navigate outside the intended file access boundaries. The vulnerability demonstrates poor secure coding practices and violates fundamental security principles of least privilege and input sanitization. According to ATT&CK framework, this vulnerability maps to T1213.002 (Data from Information Repositories) and T1566 (Phishing with Social Engineering) as attackers can use this weakness to gather intelligence for more sophisticated attacks. The exploitation process typically involves sending crafted HTTP requests that manipulate the html_url parameter to access files outside the web root directory, potentially including system configuration files, log files, and application source code that may contain sensitive information.
The operational impact of this vulnerability extends beyond simple information disclosure and can result in significant security breaches across multiple attack vectors. Once an attacker successfully exploits this vulnerability, they can obtain database connection strings, application configuration files, user credentials stored in plaintext, and source code that may reveal additional vulnerabilities. The exposure of application source code can provide attackers with detailed insights into the application architecture, potentially revealing other weaknesses such as SQL injection points, cross-site scripting vulnerabilities, or insecure cryptographic implementations. Organizations using KuaiFanCMS V5.x are at risk of data breaches, regulatory compliance violations, and reputational damage if this vulnerability remains unpatched. The vulnerability can be exploited by both authenticated and unauthenticated attackers depending on the application's configuration, making it particularly dangerous as it can be leveraged by anyone with access to the vulnerable system. This type of vulnerability is often categorized under the OWASP Top Ten as an example of insecure direct object references and can lead to privilege escalation when combined with other weaknesses in the system architecture.
Mitigation strategies for this vulnerability should focus on implementing proper input validation, access control mechanisms, and secure coding practices throughout the application. Organizations should immediately apply security patches provided by the vendor or implement custom fixes that sanitize all user input before processing, particularly parameters that are used to construct file paths. The implementation of a whitelist approach for file access, where only predetermined legitimate files can be accessed, provides an effective defense against directory traversal attacks. Additionally, enforcing proper access controls and authentication checks before allowing file access operations can significantly reduce the attack surface. Security teams should also implement network monitoring and intrusion detection systems to identify suspicious file access patterns and unauthorized attempts to exploit this vulnerability. Regular security assessments and code reviews should be conducted to identify similar weaknesses in other parts of the application. The mitigation approach aligns with NIST Cybersecurity Framework's Identify and Protect functions, emphasizing the importance of asset management and secure system design. Organizations should also consider implementing web application firewalls to detect and block malicious requests targeting this specific vulnerability, while maintaining proper logging and audit trails to monitor for exploitation attempts.