CVE-2017-1000480 in Smarty
Summary
by MITRE
Smarty 3 before 3.1.32 is vulnerable to a PHP code injection when calling fetch() or display() functions on custom resources that does not sanitize template name.
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Analysis
by VulDB Data Team • 01/20/2023
The vulnerability identified as CVE-2017-1000480 affects Smarty template engine versions prior to 3.1.32, representing a critical security flaw that enables remote code execution through improper input sanitization. This issue specifically manifests when custom resources are utilized with the fetch() or display() functions, creating a pathway for malicious actors to inject arbitrary PHP code into the application. The vulnerability stems from the template engine's failure to properly validate and sanitize template names provided through custom resource handlers, allowing attackers to manipulate the template resolution process and execute unintended code within the application context.
The technical exploitation of this vulnerability occurs through the manipulation of template names in custom resource implementations where the Smarty engine does not adequately sanitize user-supplied input before processing. When a custom resource handler is invoked with a template name that contains malicious PHP code, the lack of proper sanitization allows this code to be executed within the context of the web application. This flaw is categorized under CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and aligns with the broader category of code injection vulnerabilities that have been consistently identified as critical threats in the OWASP Top Ten. The vulnerability operates at the intersection of template processing and code execution, creating a scenario where template variables directly influence PHP code execution paths.
The operational impact of this vulnerability is severe and far-reaching, as successful exploitation can lead to complete compromise of the affected web application and underlying server infrastructure. Attackers can leverage this vulnerability to execute arbitrary PHP code, potentially gaining access to sensitive data, modifying application behavior, or establishing persistent backdoors. The attack surface is particularly concerning because it can be exploited through legitimate template engine functionality, making detection more challenging and allowing attackers to operate within normal application behavior patterns. This vulnerability directly impacts the principle of least privilege and can be used to escalate privileges within the application environment, potentially leading to full system compromise.
Mitigation strategies for CVE-2017-1000480 focus primarily on upgrading to Smarty version 3.1.32 or later, which includes proper input sanitization for template names in custom resource handlers. Organizations should also implement strict input validation policies for all template-related operations and consider implementing web application firewalls to monitor for suspicious template name patterns. The remediation process should include comprehensive code reviews to identify any custom resource handlers that may be vulnerable, along with implementing proper access controls and monitoring mechanisms. Additionally, security teams should consider implementing runtime protection measures such as PHP configuration hardening and regular security assessments to prevent exploitation of similar vulnerabilities in other components of the application stack. This vulnerability demonstrates the importance of proper input validation and sanitization in template engines, aligning with ATT&CK technique T1059.007 for PHP code injection and emphasizing the need for robust security controls in web application frameworks.