CVE-2018-5233 in Grav
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in system/src/Grav/Common/Twig/Twig.php in Grav CMS before 1.3.0 allows remote attackers to inject arbitrary web script or HTML via the PATH_INFO to admin/tools.
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Analysis
by VulDB Data Team • 01/14/2020
The vulnerability identified as CVE-2018-5233 represents a critical cross-site scripting flaw within the Grav Content Management System affecting versions prior to 1.3.0. This vulnerability resides in the system/src/Grav/Common/Twig/Twig.php file and specifically targets the handling of PATH_INFO parameters within the admin tools interface. The flaw enables remote attackers to inject malicious web scripts or HTML code through carefully crafted requests that manipulate the PATH_INFO variable, which is typically used to determine the requested resource path in web applications.
The technical implementation of this vulnerability stems from insufficient input validation and output sanitization within the Twig templating engine integration. When the Grav CMS processes administrative requests through the tools interface, it fails to properly sanitize the PATH_INFO parameter before incorporating it into the rendered HTML output. This oversight creates an opportunity for attackers to inject malicious payloads that execute in the context of other users' browsers who access the affected administrative interface. The vulnerability specifically affects the admin/tools endpoint, making it particularly dangerous as it targets the administrative functionality that typically requires elevated privileges and contains sensitive operations.
The operational impact of this vulnerability extends beyond simple script injection, as it can be leveraged for various malicious activities within the compromised environment. Attackers could potentially execute persistent XSS attacks that allow them to steal session cookies, perform unauthorized administrative actions, or redirect users to malicious domains. The vulnerability's remote exploitation capability means that attackers do not need physical access to the system or knowledge of internal network structures to exploit this flaw. Given that the administrative interface often contains sensitive data and system controls, successful exploitation could lead to complete system compromise, data exfiltration, or unauthorized modifications to the CMS configuration and content.
The vulnerability aligns with CWE-79 which defines Cross-Site Scripting as a weakness that occurs when an application includes untrusted data in a new web page without proper validation or escaping, allowing attackers to execute scripts in the victim's browser. From an adversarial perspective, this flaw maps to ATT&CK technique T1059.007 for Command and Scripting Interpreter: PowerShell, as attackers could leverage the XSS to establish persistent access through malicious scripts that execute in the browser context. The vulnerability also corresponds to ATT&CK technique T1566.001 for Initial Access: Spearphishing Attachment, as attackers could use this XSS to deliver malicious payloads through compromised administrative sessions. Organizations using vulnerable versions of Grav CMS face significant risk of unauthorized access and potential data breaches, particularly in environments where administrative interfaces are exposed to untrusted networks or where users may be targeted through social engineering attacks that exploit this vulnerability.
Mitigation strategies for CVE-2018-5233 primarily focus on immediate version upgrades to Grav CMS 1.3.0 or later, which includes proper input sanitization and output escaping mechanisms for PATH_INFO parameters. Additionally, implementing proper content security policies can provide defense-in-depth measures by restricting script execution and limiting the impact of successful XSS attempts. Organizations should also consider deploying web application firewalls that can detect and block suspicious PATH_INFO parameter patterns, while conducting regular security assessments to identify similar vulnerabilities in other components of their web applications. The implementation of proper input validation frameworks and output encoding practices across all web application components will help prevent similar issues from occurring in the future.