CVE-2017-18352 in Rendertron
Summary
by MITRE
Error reporting within Rendertron 1.0.0 allows reflected Cross Site Scripting (XSS) from invalid URLs.
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Analysis
by VulDB Data Team • 06/19/2023
The vulnerability identified as CVE-2017-18352 resides within Rendertron version 1.0.0, a server-side rendering service designed to convert web pages into static HTML for improved performance and SEO. This particular flaw manifests in the application's error reporting mechanism, which fails to properly sanitize user input when processing invalid URLs. The vulnerability specifically affects how the system handles malformed or maliciously crafted URLs that are submitted to the rendering service, creating an avenue for reflected cross site scripting attacks to occur.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding within the error handling routines of Rendertron. When users submit URLs that cannot be processed or are malformed, the system generates error messages that include the original URL as part of the error response. However, these error messages do not properly escape or encode the URL content before rendering it in the browser context. This creates a reflected XSS vector where malicious payloads embedded within the URL can be executed when the error page is displayed to users. The flaw operates under CWE-79 which classifies the weakness as "Cross-site Scripting" due to insufficient sanitization of user-provided data.
The operational impact of this vulnerability extends beyond simple script execution as it represents a critical security risk for any application utilizing Rendertron for server-side rendering. Attackers can craft malicious URLs containing JavaScript payloads that will execute in the context of authenticated users who view the error pages generated by the vulnerable system. This could lead to session hijacking, credential theft, or redirection to malicious sites. The reflected nature of the vulnerability means that successful exploitation requires user interaction with a specifically crafted URL, typically through phishing campaigns or social engineering tactics. The attack vector aligns with ATT&CK technique T1566 which covers social engineering methods to gain initial access, while the execution component maps to T1059 which covers command and scripting interpreter usage.
Mitigation strategies for CVE-2017-18352 require immediate implementation of proper input validation and output encoding practices within the Rendertron error handling components. Organizations should ensure that all user-provided input, particularly URLs, undergo proper sanitization before being included in error messages or displayed to end users. The recommended approach involves implementing strict URL validation routines that reject malformed inputs and applying HTML encoding to any user-supplied content that must be rendered in error responses. Additionally, implementing content security policies and using modern security headers can provide additional defense in depth. The vulnerability serves as a reminder of the critical importance of proper input validation in web applications, particularly those handling user-provided URLs and serving as intermediaries in web content processing. Organizations should also consider upgrading to newer versions of Rendertron where this vulnerability has been addressed, as version 1.0.0 represents an outdated release that likely contains multiple unpatched security issues. The remediation process should include comprehensive testing to ensure that all error paths properly handle user input without introducing XSS vulnerabilities, and regular security assessments should be conducted to identify similar issues in other components of the application stack.