CVE-2017-18354 in Rendertron
Summary
by MITRE
Rendertron 1.0.0 allows for alternative protocols such as 'file://' introducing a Local File Inclusion (LFI) bug where arbitrary files can be read by a remote attacker.
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Analysis
by VulDB Data Team • 06/19/2023
The vulnerability identified as CVE-2017-18354 resides within Rendertron version 1.0.0, a server-side rendering service that converts web pages into static HTML for improved SEO and performance. This issue manifests as a local file inclusion flaw that stems from inadequate protocol validation within the application's handling of web requests. The vulnerability enables remote attackers to exploit the system by crafting malicious requests that leverage alternative protocols such as 'file://' which bypass normal security boundaries. This represents a critical security weakness that fundamentally undermines the isolation mechanisms typically enforced by web applications.
The technical implementation of this vulnerability occurs when Rendertron processes incoming requests and fails to properly validate or sanitize the protocol schemes used in URLs. When a user submits a request containing a 'file://' URI scheme, the application does not adequately restrict or filter these alternative protocols, allowing the system to attempt to read local files from the server's filesystem. This flaw operates at the application layer where input validation should prevent such protocol switching, but instead permits direct access to the underlying operating system file structure. The vulnerability directly maps to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks.
From an operational perspective, this vulnerability creates significant risk for organizations utilizing Rendertron 1.0.0 as their server-side rendering solution. Remote attackers can leverage this weakness to access sensitive files including configuration data, database credentials, application source code, and other system artifacts that should remain isolated from external access. The impact extends beyond simple information disclosure as attackers could potentially gather intelligence about the system architecture, identify other vulnerabilities, or even escalate their access to compromise the entire server environment. This vulnerability represents a classic attack vector that aligns with techniques documented in the attack pattern taxonomy under the MITRE ATT&CK framework, specifically relating to credential access and reconnaissance activities.
The mitigation strategy for CVE-2017-18354 requires immediate implementation of proper input validation and protocol restriction within the Rendertron application. Organizations should ensure that all incoming URLs are strictly validated to prevent the use of alternative protocols such as 'file://', 'ftp://', or other potentially dangerous schemes. The fix should involve implementing a whitelist approach that only permits safe protocol schemes such as 'http://' and 'https://'. Additionally, system administrators should consider implementing network-level restrictions and firewall rules to prevent access to the Rendertron service from untrusted networks. Regular security auditing and input validation testing should be conducted to prevent similar issues from emerging in other components of the application stack. The vulnerability demonstrates the critical importance of proper input sanitization and protocol handling in web applications, reinforcing industry best practices that align with secure coding standards and defensive programming principles.