CVE-2015-7579 in Ruby on Rails
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the rails-html-sanitizer gem 1.0.2 for Ruby on Rails 4.2.x and 5.x allows remote attackers to inject arbitrary web script or HTML via an HTML entity that is mishandled by the Rails::Html::FullSanitizer class.
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Analysis
by VulDB Data Team • 07/06/2022
The CVE-2015-7579 vulnerability represents a critical cross-site scripting flaw within the rails-html-sanitizer gem version 1.0.2, affecting Ruby on Rails 4.2.x and 5.x applications. This vulnerability specifically targets the Rails::Html::FullSanitizer class which is responsible for sanitizing HTML content to prevent malicious script injection. The flaw arises from improper handling of HTML entities during the sanitization process, creating a pathway for remote attackers to bypass security measures and execute arbitrary web scripts or HTML code within victim browsers.
The technical implementation of this vulnerability stems from the gem's insufficient parsing and sanitization logic when processing HTML entities. When the Rails::Html::FullSanitizer encounters certain malformed HTML entities, it fails to properly escape or remove these elements, allowing malicious payloads to persist in the sanitized output. This misconfiguration creates a condition where attackers can craft input containing specially formatted HTML entities that, when processed by the sanitizer, are not adequately neutralized. The vulnerability operates at the application layer and can be exploited through user input fields, comment sections, or any endpoint that accepts and processes HTML content without proper validation.
The operational impact of CVE-2015-7579 extends beyond simple script execution, as it enables attackers to perform session hijacking, defacement of web applications, data theft, and redirection to malicious sites. When exploited successfully, this vulnerability allows remote code execution within the context of a victim's browser, potentially leading to complete compromise of user sessions and sensitive data exposure. Applications using affected versions of the rails-html-sanitizer gem become vulnerable to persistent XSS attacks where malicious scripts can execute automatically when users view compromised content, making this vulnerability particularly dangerous in web applications where user-generated content is common.
Organizations should immediately upgrade to versions of the rails-html-sanitizer gem that address this vulnerability, typically versions 1.0.3 or later, which contain proper HTML entity handling and sanitization routines. Additionally, implementing proper input validation, output encoding, and Content Security Policy headers can provide additional defense-in-depth measures. This vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and maps to ATT&CK technique T1059.001 for command and scripting interpreter usage. Security teams should conduct comprehensive vulnerability assessments across all Ruby on Rails applications using affected gem versions and implement automated monitoring to detect potential exploitation attempts. The remediation process should include thorough testing of the updated gem in staging environments to ensure compatibility and prevent regression issues in existing application functionality.