CVE-2018-6184 in Next.js
Summary
by MITRE
ZEIT Next.js 4 before 4.2.3 has Directory Traversal under the /_next request namespace.
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Analysis
by VulDB Data Team • 02/02/2023
The vulnerability identified as CVE-2018-6184 affects ZEIT Next.js version 4.2.2 and earlier, specifically within the /_next request namespace handling. This directory traversal flaw represents a critical security weakness that allows attackers to access files and directories outside the intended application scope. The vulnerability manifests when the application processes requests directed to the /_next namespace, which is typically used for serving static assets and internal application resources. The flaw stems from insufficient input validation and path sanitization mechanisms within the framework's routing and file serving components, creating an opportunity for malicious actors to manipulate request paths and gain unauthorized access to sensitive system resources.
The technical implementation of this vulnerability involves the improper handling of user-supplied input within the request processing pipeline for the /_next namespace. When Next.js receives a request to access resources within this namespace, the application fails to properly validate or sanitize the requested path components, allowing attackers to inject directory traversal sequences such as ../ or ..\ to navigate outside the intended document root or application directory. This weakness enables attackers to potentially access server configuration files, source code, environment variables, or other sensitive data that should remain protected from external access. The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. This type of vulnerability is particularly dangerous in web applications because it can lead to complete system compromise when combined with other attack vectors.
The operational impact of CVE-2018-6184 extends beyond simple data exposure, as it provides attackers with the capability to escalate privileges and potentially execute arbitrary code on the affected server. Attackers can leverage this vulnerability to access not only static assets but also dynamic application resources that should remain protected. The attack surface includes potential access to sensitive configuration files, database credentials, API keys, and other confidential information that could be stored in the application's directory structure. In environments where Next.js applications are deployed with elevated privileges or where sensitive data is stored in predictable paths, this vulnerability could enable full system compromise. The vulnerability also affects the principle of least privilege, as it allows unauthorized access to resources that should be restricted to authorized users or processes.
Mitigation strategies for this vulnerability require immediate application updates to version 4.2.3 or later, where the directory traversal protection mechanisms have been implemented. Organizations should also implement additional security controls including input validation at multiple layers, proper path sanitization, and access control restrictions for the /_next namespace. Network-level protections such as web application firewalls and intrusion detection systems can help detect and block malicious traversal attempts. The remediation process should include comprehensive security testing of all application components and regular vulnerability assessments to identify similar weaknesses. Security teams should also consider implementing the principle of least privilege for application deployments, ensuring that application processes run with minimal required permissions and that sensitive files are properly secured. This vulnerability highlights the importance of proper input validation and access control implementation in web frameworks, aligning with ATT&CK technique T1083 for discovering system information and T1213 for data from information repositories.