CVE-2018-11322 in Joomla
Summary
by MITRE
An issue was discovered in Joomla! Core before 3.8.8. Depending on the server configuration, PHAR files might be handled as executable PHP scripts by the webserver.
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Analysis
by VulDB Data Team • 03/14/2023
The vulnerability identified as CVE-2018-11322 represents a critical server-side misconfiguration issue within Joomla! Core versions prior to 3.8.8 that exposes systems to potential remote code execution risks. This flaw stems from improper handling of PHAR (PHP Archive) files by web servers, creating a dangerous scenario where maliciously crafted archive files could be interpreted and executed as PHP scripts rather than being treated as binary data. The vulnerability specifically affects installations where server configurations do not properly restrict PHAR file execution, allowing attackers to leverage this misconfiguration for unauthorized code execution.
The technical root cause of this vulnerability lies in the web server's file handling behavior and the absence of proper content type validation for PHAR files. When a PHAR file is uploaded or accessed through a vulnerable Joomla! installation, the web server may interpret the file's content as executable PHP code instead of recognizing it as a serialized archive. This misinterpretation occurs due to server-level configuration issues where the .phar file extension is not properly restricted or where the server's MIME type handling does not prevent PHAR files from being executed as PHP scripts. The vulnerability essentially creates an execution path where attacker-controlled PHAR files can be processed through the PHP interpreter, bypassing normal file access controls and security boundaries.
The operational impact of this vulnerability is severe and can result in complete system compromise when exploited successfully. Attackers can upload malicious PHAR files that contain PHP code designed to execute arbitrary commands on the server, potentially leading to full system takeover, data exfiltration, or persistent backdoor installation. The vulnerability affects any Joomla! installation running versions earlier than 3.8.8 where the web server configuration allows PHAR files to be executed, making it particularly dangerous for publicly accessible web applications. The risk is amplified when the server configuration does not properly implement security headers or file type restrictions that would normally prevent such execution paths.
This vulnerability aligns with CWE-434, which addresses the improper restriction of file uploads, and represents a classic case of insecure file handling that can lead to remote code execution. The attack vector typically involves uploading a malicious PHAR file through Joomla!'s file upload mechanisms or by exploiting other vulnerabilities that allow file placement on the server. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for PHP and T1078 for valid accounts, as it enables adversaries to execute code using legitimate PHP processing capabilities. The vulnerability also relates to T1566 for malicious file execution and T1021.004 for remote services, as it allows attackers to leverage web server capabilities for code execution.
Mitigation strategies for CVE-2018-11322 should focus on both immediate patching and configuration hardening. The primary solution involves upgrading to Joomla! Core version 3.8.8 or later, which includes proper file handling and validation mechanisms that prevent PHAR files from being executed as PHP scripts. Additionally, system administrators should implement server-level restrictions that prevent PHAR files from being processed by PHP interpreters, including proper MIME type configurations, file extension restrictions, and security headers that prevent execution of archive files. Network-level controls such as web application firewalls can also help detect and block suspicious PHAR file access patterns. Organizations should also conduct regular security audits of their server configurations to ensure that file handling behaviors align with security best practices and that no unintended execution paths exist for archive files.