CVE-2021-27230 in ExpressionEngine
Summary
by MITRE • 03/16/2021
ExpressionEngine before 5.4.2 and 6.x before 6.0.3 allows PHP Code Injection by certain authenticated users who can leverage Translate::save() to write to an _lang.php file under the system/user/language directory.
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Analysis
by VulDB Data Team • 06/29/2024
ExpressionEngine versions prior to 5.4.2 and 6.x prior to 6.0.3 contain a critical php code injection vulnerability that stems from inadequate input validation within the Translate::save() method. This flaw enables authenticated users with sufficient privileges to execute arbitrary php code on the affected system by manipulating the language translation functionality. The vulnerability specifically occurs when the application writes translation data to _lang.php files located in the system/user/language directory, creating a path traversal and code injection vector.
The technical implementation of this vulnerability involves the Translate::save() function failing to properly sanitize user-supplied input before incorporating it into php code files. When authenticated users with access to the translation management interface submit malicious input containing php code, the application processes this data without adequate validation or escaping mechanisms. This results in the injection of executable php code into the _lang.php files, which are subsequently loaded and executed by the php interpreter during application runtime. The vulnerability operates under CWE-94, which describes improper control of generation of code, and aligns with ATT&CK technique T1505.003 for PHP code injection.
The operational impact of this vulnerability is severe as it allows attackers to escalate privileges from authenticated user access to full system compromise. Once exploited, the injected php code can perform arbitrary operations including but not limited to data exfiltration, privilege escalation, web shell deployment, and persistence mechanisms. The vulnerability affects organizations running vulnerable ExpressionEngine installations where translation functionality is enabled and accessible to users with appropriate permissions. Attackers can leverage this vulnerability to gain unauthorized access to sensitive data, modify application behavior, and potentially establish persistent backdoors within the affected environment.
Mitigation strategies for this vulnerability include immediate upgrade to ExpressionEngine versions 5.4.2 or 6.0.3, which contain patches addressing the input validation flaws in the Translate::save() method. Organizations should also implement network segmentation to limit access to translation management interfaces and enforce strict access controls for users with elevated privileges. Additionally, monitoring for unusual file modifications in the system/user/language directory can help detect potential exploitation attempts. The fix implemented in patched versions typically involves implementing proper input sanitization, output escaping, and validation mechanisms to prevent malicious code from being written to php files during translation save operations. Security teams should also consider implementing application firewalls and web application security monitoring to detect and prevent exploitation attempts targeting this specific vulnerability.