CVE-2021-44618 in Seomatic
Summary
by MITRE • 03/11/2022
A Server-side Template Injection (SSTI) vulnerability exists in Nystudio107 Seomatic 3.4.12 in src/helpers/UrlHelper.php via the host header.
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Analysis
by VulDB Data Team • 03/14/2022
The Server-Side Template Injection vulnerability identified as CVE-2021-44618 represents a critical security flaw within the Nystudio107 Seomatic plugin version 3.4.12, specifically manifesting in the src/helpers/UrlHelper.php file. This vulnerability arises from improper handling of the host header parameter, which allows malicious actors to inject template code that gets executed on the server side. The issue stems from the plugin's failure to properly sanitize or validate input derived from HTTP headers, creating an attack surface where crafted host header values can be processed through template rendering mechanisms. Such vulnerabilities are particularly dangerous because they can enable attackers to execute arbitrary code on the affected server, potentially leading to complete system compromise.
The technical exploitation of this SSTI vulnerability occurs when an attacker manipulates the HTTP host header to include template syntax that the application's URL helper processes without adequate sanitization. This flaw allows attackers to inject malicious template code that gets rendered and executed on the server, bypassing normal input validation controls. The vulnerability is classified under CWE-94, which specifically addresses "Improper Control of Generation of Code ('Code Injection')" and aligns with ATT&CK technique T1505.003 for "Server-side Template Injection." The host header manipulation exploits the trust relationship between the web server and the application, leveraging the fact that many applications treat host header values as trusted input for URL generation and processing.
The operational impact of this vulnerability extends beyond simple code execution, as it can enable attackers to perform various malicious activities including data exfiltration, privilege escalation, and persistent backdoor installation. An attacker who successfully exploits this vulnerability can gain unauthorized access to the web application's underlying system, potentially accessing sensitive data stored in the database or file system. The severity is compounded by the fact that this vulnerability affects the URL helper functionality, which is likely used throughout the application for generating canonical URLs, redirects, and other web navigation elements, making it a high-value target for exploitation. The attack surface is particularly concerning because host header manipulation is a common technique used in various web application attacks and is often overlooked during security assessments.
Mitigation strategies for CVE-2021-44618 should focus on immediate patching of the Nystudio107 Seomatic plugin to version 3.4.13 or later, which contains the necessary fixes for the template injection vulnerability. Organizations should implement strict input validation and sanitization for all host header values, ensuring that any template syntax is properly escaped or removed before processing. Network-level protections including web application firewalls and host header validation rules can provide additional defense in depth. Security monitoring should include detection of unusual host header patterns and template syntax in application logs. The vulnerability highlights the importance of proper secure coding practices, particularly around template handling and input validation, as recommended by OWASP Top 10 and ISO/IEC 27001 security standards. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other application components that might be susceptible to similar template injection attacks.