CVE-2023-34251 in Grav
Summary
by MITRE • 06/15/2023
Grav is a flat-file content management system. Versions prior to 1.7.42 are vulnerable to server side template injection. Remote code execution is possible by embedding malicious PHP code on the administrator screen by a user with page editing privileges. Version 1.7.42 contains a fix for this issue.
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Analysis
by VulDB Data Team • 07/13/2023
Grav represents a flat-file content management system that operates without traditional database dependencies, relying instead on file-based storage for its content management operations. This architecture presents unique security considerations as the system must properly validate and sanitize all user inputs to prevent malicious code execution. The vulnerability described in CVE-2023-34251 specifically targets the template rendering engine of Grav versions prior to 1.7.42, creating a server-side template injection flaw that enables remote code execution under specific conditions. The vulnerability manifests when administrators or users with page editing privileges inadvertently introduce malicious PHP code into the system through the content management interface.
The technical flaw stems from insufficient input validation and sanitization within the template processing components of Grav's core framework. When users with editing privileges create or modify pages containing specially crafted template code, the system fails to properly escape or filter the input before rendering it within the server-side template context. This allows attackers to inject malicious PHP code that executes on the server with the privileges of the web application process. The vulnerability operates as a server-side template injection because the system processes user-supplied template variables without adequate protection mechanisms, enabling code execution through the template engine's interpretation of malformed input.
The operational impact of this vulnerability extends beyond simple data compromise as it provides attackers with full remote code execution capabilities on the affected server. An attacker with page editing privileges can inject PHP payloads that execute arbitrary commands, potentially leading to complete system compromise, data exfiltration, or further lateral movement within the network. The attack vector requires minimal privileges, making it particularly dangerous as it can be exploited by users who should normally have limited access to system functions. This vulnerability aligns with CWE-94, which describes improper control of generation of code, specifically highlighting the dangerous combination of template processing and insufficient input sanitization.
The exploitation scenario typically involves an attacker with page editing permissions who crafts malicious content that gets processed through the template engine, executing code on the server. This represents a privilege escalation attack pattern that can be classified under ATT&CK technique T1059.007 for command and script injection. The vulnerability affects organizations using outdated Grav installations, particularly those with multiple users who have editing privileges, as the attack requires only the ability to modify content rather than administrative access to the system. The fix implemented in version 1.7.42 addresses this by strengthening input validation and implementing proper template escaping mechanisms.
Organizations should immediately upgrade to Grav version 1.7.42 or later to remediate this vulnerability and prevent potential exploitation. System administrators should also implement additional monitoring for unusual content modifications and review user access permissions to limit the scope of potential attacks. The vulnerability demonstrates the importance of proper input validation in web applications and highlights how template engines can become attack vectors when not properly secured against user-supplied content. Security teams should also consider implementing web application firewalls and content filtering mechanisms to detect and block suspicious template injection attempts. This vulnerability serves as a reminder that even seemingly benign content management systems can present significant security risks when template processing lacks proper sanitization controls.