CVE-2012-4437 in Smarty
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the SmartyException class in Smarty (aka smarty-php) before 3.1.12 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors that trigger a Smarty exception.
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Analysis
by VulDB Data Team • 12/14/2021
The CVE-2012-4437 vulnerability represents a critical cross-site scripting flaw within the Smarty template engine framework that affected versions prior to 3.1.12. This vulnerability resides in the SmartyException class and creates a pathway for remote attackers to inject malicious web scripts or HTML content through unspecified vectors that trigger exception handling mechanisms. The vulnerability is particularly concerning because it leverages the normal exception handling process of the template engine to execute arbitrary code in the context of a victim's browser, potentially leading to session hijacking, credential theft, or other malicious activities.
The technical nature of this vulnerability stems from inadequate input sanitization within the SmartyException class when processing error conditions. When the Smarty template engine encounters an error, it generates exceptions that are subsequently rendered in the output, creating an injection point where attacker-controlled data can be executed as script code. This flaw operates under the CWE-79 category of Cross-Site Scripting, specifically manifesting as a stored or reflected XSS vulnerability depending on how the malicious input is processed and displayed. The vulnerability demonstrates a classic weakness in the principle of least privilege and proper input validation, where user-supplied data flows directly into the output without appropriate sanitization or encoding.
The operational impact of this vulnerability extends beyond simple script injection to potentially compromise entire web applications built on the Smarty framework. Attackers can exploit this weakness to execute malicious scripts in the context of authenticated users, potentially leading to full account compromise, data exfiltration, or the establishment of backdoors within the affected systems. The vulnerability affects web applications that utilize Smarty for template rendering and are vulnerable to attacks targeting the exception handling mechanism. This creates a significant risk for content management systems, web applications, and frameworks that rely on Smarty for dynamic content generation, as the attack surface expands to include all areas where user input might trigger template exceptions.
Organizations should implement immediate mitigations including upgrading to Smarty version 3.1.12 or later, which contains the necessary patches to address the XSS vulnerability. Additionally, implementing proper input validation and output encoding mechanisms can provide defense-in-depth measures against similar vulnerabilities. Security teams should conduct comprehensive assessments of applications using Smarty to identify potential injection points and ensure that all user-supplied data is properly sanitized before processing. The vulnerability highlights the importance of secure coding practices and proper exception handling in web applications, aligning with ATT&CK technique T1566 for initial access through malicious inputs and T1059 for command and scripting interpreter execution. Regular security testing including dynamic application security testing and static code analysis should be implemented to identify similar vulnerabilities in the application's codebase.