CVE-2018-20166 in Rukovoditel
Summary
by MITRE
A file-upload vulnerability exists in Rukovoditel 2.3.1. index.php?module=configuration/save allows the user to upload a background image, and mishandles extension checking. It accepts uploads of PHP content if the first few characters match GIF data, and the filename ends in ".php" with mixed case, such as the .pHp extension.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/03/2025
The vulnerability identified as CVE-2018-20166 represents a critical file upload flaw in Rukovoditel version 2.3.1 that undermines the application's security controls through inadequate input validation. This weakness resides within the configuration module's save functionality at index.php?module=configuration/save where users can upload background images for the application interface. The vulnerability stems from a flawed file extension validation mechanism that fails to properly enforce security checks on uploaded files, creating an avenue for malicious actors to bypass intended restrictions.
The technical implementation of this vulnerability exploits a combination of file signature inspection and filename extension handling that creates a dangerous overlap in the validation process. The system performs a basic check on the initial bytes of uploaded files to verify they match GIF format signatures, but this check is insufficient to prevent execution of malicious code. Attackers can leverage this by crafting files where the first few bytes contain valid GIF header data while the filename ends with a php extension in mixed case such as .pHp. This approach allows the system to accept the file as a valid image based on the initial signature check while simultaneously permitting execution of the PHP code due to the filename extension validation being bypassed.
This vulnerability directly maps to CWE-434, which describes insecure file upload vulnerabilities where applications accept files without proper validation of file type and content. The flaw creates a path for remote code execution attacks as the uploaded PHP files can be executed by the web server when accessed through the application's interface. The mixed case extension bypass technique demonstrates a failure in implementing consistent and comprehensive input validation, which is a fundamental security principle that aligns with the NIST SP 800-161 standard for secure coding practices. The vulnerability also relates to ATT&CK technique T1505.003 for server-side include attacks and T1059.007 for scripting languages, as it enables attackers to execute malicious code through PHP files.
The operational impact of this vulnerability is significant as it allows attackers to gain unauthorized code execution capabilities within the application environment. Successful exploitation could enable attackers to upload malicious PHP shells, backdoor scripts, or other malicious payloads that could be used to establish persistent access to the system. This vulnerability affects the integrity and confidentiality of the application's data and potentially the underlying infrastructure, as attackers could use the compromised system to pivot to other network resources. The vulnerability's impact is amplified by the fact that it requires minimal privileges to exploit, as the upload functionality is typically available to authenticated users, making it particularly dangerous in environments where user access controls are not properly implemented.
Mitigation strategies should focus on implementing robust file validation mechanisms that examine both file content and extension in a consistent manner. The recommended approach includes implementing strict file type validation that checks against a whitelist of allowed MIME types and extensions, while also validating the actual file content against expected signatures rather than relying solely on filename extensions. Organizations should also implement proper file naming conventions that prevent mixed-case extensions and enforce consistent case usage for all file extensions. Additionally, uploaded files should be stored in a separate directory from the web root with restricted permissions to prevent direct execution of uploaded content. The implementation should follow the principle of least privilege and include proper logging and monitoring of file upload activities to detect potential exploitation attempts. Regular security testing and code reviews should be conducted to identify similar vulnerabilities in other application components and ensure that file upload functionality adheres to established security frameworks and best practices.