CVE-2018-16468 in Loofah Gem
Summary
by MITRE
In the Loofah gem for Ruby, through v2.2.2, unsanitized JavaScript may occur in sanitized output when a crafted SVG element is republished.
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Analysis
by VulDB Data Team • 06/03/2023
The vulnerability CVE-2018-16468 affects the Loofah gem version 2.2.2 and earlier, representing a critical security flaw in HTML sanitization functionality. This issue specifically manifests when processing SVG elements containing crafted malicious content that bypasses the sanitization process, potentially allowing arbitrary JavaScript execution in vulnerable applications. The vulnerability stems from insufficient validation of SVG attributes and elements within the sanitization pipeline, creating a path for attackers to inject malicious code that would normally be filtered out.
The technical flaw exists within the HTML sanitization logic of the Loofah gem where SVG elements are not properly validated against security constraints. When a crafted SVG element contains JavaScript within attributes or child elements, the sanitization process fails to adequately strip or escape these dangerous components. This vulnerability is particularly concerning because SVG elements can contain script tags, event handlers, and other potentially malicious constructs that are not properly handled by the current sanitization rules. The flaw operates at the level of HTML attribute sanitization and element validation, where the system incorrectly assumes that SVG elements are safe when they contain potentially dangerous content.
The operational impact of this vulnerability is significant for applications that rely on Loofah for HTML sanitization, particularly those processing user-generated content or external data sources. Attackers could exploit this weakness by injecting malicious SVG content that, when rendered, executes unauthorized JavaScript code in the context of the victim's browser. This could lead to session hijacking, data theft, cross-site scripting attacks, and potential privilege escalation within affected applications. The vulnerability affects web applications that use Ruby on Rails or other frameworks that depend on Loofah for content sanitization, making it a widespread concern across numerous production environments.
Organizations should immediately upgrade to Loofah version 2.2.3 or later, which contains the necessary patches to address this vulnerability. The fix implemented by the maintainers involves strengthening the SVG sanitization rules and ensuring that all JavaScript-related attributes and elements are properly escaped or removed during the sanitization process. Security teams should conduct thorough code reviews to identify any instances where Loofah is used for HTML sanitization and verify that all user-provided content is properly validated. Additionally, implementing additional security layers such as content security policies and regular security testing can help mitigate potential exploitation attempts.
This vulnerability maps to CWE-79 in the Common Weakness Enumeration catalog, which specifically addresses Cross-Site Scripting (XSS) vulnerabilities in web applications. The weakness occurs due to insufficient sanitization of user-provided data, particularly when dealing with complex HTML elements like SVG that contain multiple attribute types and scripting capabilities. From the MITRE ATT&CK framework perspective, this vulnerability aligns with the T1059.007 technique related to JavaScript execution and the T1203 technique for exploitation of web application vulnerabilities. The attack vector typically involves injecting malicious SVG content through web forms, file uploads, or API endpoints where user input is processed without proper validation, making it a prime target for automated exploitation tools and manual attack campaigns.