CVE-2008-4810 in Smarty
Summary
by MITRE
The _expand_quoted_text function in libs/Smarty_Compiler.class.php in Smarty 2.6.20 before r2797 allows remote attackers to execute arbitrary PHP code via vectors related to templates and (1) a dollar-sign character, aka "php executed in templates;" and (2) a double quoted literal string, aka a "function injection security hole." NOTE: each vector affects slightly different SVN revisions.
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Analysis
by VulDB Data Team • 08/21/2019
The vulnerability identified as CVE-2008-4810 represents a critical remote code execution flaw within the Smarty template engine version 2.6.20 and earlier releases. This security issue resides in the _expand_quoted_text function located within the libs/Smarty_Compiler.class.php file, which serves as the core compilation component responsible for processing template files. The vulnerability stems from insufficient input validation and sanitization mechanisms that fail to properly handle user-supplied template data, creating opportunities for attackers to inject malicious PHP code that gets executed during template compilation.
The technical exploitation occurs through two distinct but related attack vectors that leverage different aspects of Smarty's template parsing mechanisms. The first vector involves the manipulation of template content through dollar-sign characters, which allows attackers to inject PHP code that gets executed within the template context. The second vector targets double-quoted literal strings in templates, creating what is termed a "function injection security hole" where malicious code can be injected into function calls. Both attack paths exploit the lack of proper escaping and validation when processing template variables and expressions, particularly when these elements contain untrusted user input that bypasses normal security checks during the compilation phase.
The operational impact of this vulnerability is severe and far-reaching, as it enables remote attackers to execute arbitrary PHP code on affected systems without requiring authentication or prior access. This creates a complete compromise scenario where attackers can gain full control over the web server running the vulnerable Smarty application. The vulnerability affects various SVN revisions, with different attack vectors impacting slightly different versions, which complicates the remediation process and requires careful version tracking. Systems utilizing Smarty for template rendering, including content management systems, web applications, and frameworks that depend on this library, become immediately vulnerable to code execution attacks that can lead to data breaches, system compromise, and unauthorized access to sensitive information.
The vulnerability aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and corresponds to ATT&CK technique T1190, "Exploit Public-Facing Application," highlighting the exposure of web applications to remote code execution through template injection. Organizations using affected versions of Smarty should immediately implement mitigations including upgrading to patched versions, implementing proper input validation and sanitization, restricting template file permissions, and employing web application firewalls to detect and block malicious template injection attempts. The vulnerability demonstrates the critical importance of secure template processing and the potential consequences when template engines fail to properly handle untrusted input data, making it a prime example of how template injection flaws can lead to complete system compromise.