CVE-2019-7743 in Joomla
Summary
by MITRE
An issue was discovered in Joomla! before 3.9.3. The phar:// stream wrapper can be used for objection injection attacks because there is no protection mechanism (such as the TYPO3 PHAR stream wrapper) to prevent use of the phar:// handler for non .phar-files.
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Analysis
by VulDB Data Team • 05/31/2020
The vulnerability identified as CVE-2019-7743 represents a critical security flaw in Joomla installations by allowing attackers to manipulate how files are processed through the stream wrapper functionality.
The technical flaw manifests through the improper handling of the phar:// protocol within Joomla allows attackers to construct malicious file paths that can bypass normal file validation checks and execute arbitrary code through object injection attacks. This vulnerability operates at the core of the application's file handling architecture and demonstrates a fundamental failure in input sanitization.
The operational impact of CVE-2019-7743 extends far beyond simple code execution, as it provides attackers with a pathway to achieve persistent access and data compromise within affected Joomla! environments. Successful exploitation can lead to complete system compromise, allowing attackers to upload additional malicious payloads, establish backdoors, or exfiltrate sensitive data from database connections and user accounts. The vulnerability is particularly dangerous because it can be leveraged through multiple attack vectors including file upload forms, URL parameters, and file inclusion mechanisms that rely on the phar:// stream wrapper. This makes it difficult to detect and mitigate, as the attack can occur through seemingly legitimate application functionality while maintaining stealth.
Security professionals should consider this vulnerability in the context of broader software security practices and the specific protections recommended by industry standards such as CWE-502 which addresses deserialization vulnerabilities, and ATT&CK techniques related to code injection and privilege escalation. The lack of proper stream wrapper validation represents a failure in the principle of least privilege and proper input validation. Organizations should immediately upgrade to Joomla! version 3.9.3 or later to address this vulnerability, while implementing additional network-based controls such as web application firewalls and monitoring for suspicious phar:// URI patterns. The vulnerability also highlights the importance of proper security testing and code review practices, particularly when implementing stream wrapper functionality that interacts with user-supplied data.