CVE-2018-19422 in Subrion CMS
Summary
by MITRE
/panel/uploads in Subrion CMS 4.2.1 allows remote attackers to execute arbitrary PHP code via a .pht or .phar file, because the .htaccess file omits these.
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Analysis
by VulDB Data Team • 08/04/2025
The vulnerability identified as CVE-2018-19422 represents a critical security flaw in Subrion CMS version 4.2.1 that exposes the system to remote code execution attacks. This issue stems from improper file extension handling within the upload functionality of the admin panel, specifically in the /panel/uploads directory. The vulnerability allows attackers to bypass security restrictions by uploading malicious PHP files with extensions that are not properly blocked by the server configuration.
The technical root cause of this vulnerability lies in the incomplete filtering of file extensions within the .htaccess configuration file. The security mechanism fails to explicitly block .pht and .phar file extensions, which are valid PHP file formats that can execute code when processed by the web server. These extensions are particularly dangerous because they can be interpreted by PHP as executable scripts even when placed in directories that should be restricted. The .pht extension is a legitimate PHP file extension that is often used for PHP files, while .phar files are PHP archive files that can contain executable PHP code and are commonly used for packaging PHP applications.
This vulnerability creates a significant operational impact as it enables remote attackers to gain unauthorized access to the system and execute arbitrary commands with the privileges of the web server. The attack vector is straightforward and requires minimal technical expertise to exploit, making it particularly dangerous in production environments. Successful exploitation could lead to complete system compromise, data theft, or the installation of backdoors that persist even after system updates. The vulnerability affects any system running Subrion CMS 4.2.1 where the upload functionality is accessible to unauthenticated users or where administrative privileges can be obtained through other means.
The security implications extend beyond simple code execution to encompass broader system compromise and potential lateral movement within network environments. Attackers could leverage this vulnerability to establish persistent access, escalate privileges, or use the compromised system as a launch point for attacking other systems. This weakness aligns with CWE-434 which describes "Unrestricted Upload of File with Dangerous Type" and represents a classic example of insufficient input validation and access control. From an ATT&CK framework perspective, this vulnerability maps to T1190 "Exploit Public-Facing Application" and T1059 "Command and Scripting Interpreter" as it allows for command execution through web application exploitation.
Organizations affected by this vulnerability should implement immediate mitigations including updating to a patched version of Subrion CMS, modifying the .htaccess file to explicitly block .pht and .phar extensions, and implementing additional upload restrictions. The recommended approach involves ensuring that all potentially dangerous file extensions are explicitly denied in server configuration files and that proper file type validation occurs both on the client and server sides. Additionally, implementing proper access controls and monitoring for unusual upload activities can help detect exploitation attempts. Security teams should also consider implementing network-level restrictions to prevent access to the upload directory from unauthorized networks and ensure that all systems are regularly updated to address known vulnerabilities.