CVE-2011-2932 in Ruby on Rails
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in activesupport/lib/active_support/core_ext/string/output_safety.rb in Ruby on Rails 2.x before 2.3.13, 3.0.x before 3.0.10, and 3.1.x before 3.1.0.rc5 allows remote attackers to inject arbitrary web script or HTML via a malformed Unicode string, related to a "UTF-8 escaping vulnerability."
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Analysis
by VulDB Data Team • 11/18/2021
The CVE-2011-2932 vulnerability represents a critical cross-site scripting flaw in the Ruby on Rails web application framework that affected multiple version branches including 2.x before 2.3.13, 3.0.x before 3.0.10, and 3.1.x before 3.1.0.rc5. This vulnerability specifically targets the activesupport component's core_ext/string/output_safety.rb file, which handles string output sanitization and escaping mechanisms. The flaw arises from improper handling of malformed Unicode strings during UTF-8 escaping operations, creating a pathway for remote attackers to inject malicious web scripts or HTML content into web applications built on the affected Rails versions.
The technical nature of this vulnerability stems from a fundamental flaw in how Rails processed UTF-8 encoded strings when escaping output for web display. When developers used Rails' built-in escaping mechanisms to sanitize user input before rendering it in web pages, the framework failed to properly handle certain malformed Unicode sequences. This weakness allowed attackers to craft specially crafted input containing Unicode characters that would bypass the intended escaping logic, ultimately resulting in the execution of malicious scripts in the context of victim browsers. The vulnerability operates at the core string handling level, making it particularly dangerous as it affects the fundamental security controls that applications rely upon to prevent XSS attacks.
The operational impact of CVE-2011-2932 extends far beyond simple script injection, as it can enable attackers to perform a wide range of malicious activities including session hijacking, data theft, and redirection to malicious sites. Applications using affected Rails versions become vulnerable to attacks where an attacker could inject JavaScript code that steals cookies, session tokens, or other sensitive information from users interacting with the compromised application. The vulnerability is particularly concerning because it affects widely deployed web applications, and the exploitation requires minimal skill level, making it attractive to both automated attacks and targeted campaigns. Organizations running vulnerable Rails applications faced significant risk of data breaches and compromised user sessions, especially in applications handling sensitive user information or financial transactions.
Mitigation strategies for CVE-2011-2932 primarily involve upgrading to patched versions of Ruby on Rails, specifically versions 2.3.13, 3.0.10, and 3.1.0.rc5 or later, which contain proper UTF-8 escaping mechanisms. Security teams should also implement additional defensive measures including comprehensive input validation, content security policies, and regular security audits of web applications. Organizations should consider implementing web application firewalls and monitoring systems to detect potential exploitation attempts. The vulnerability aligns with CWE-79, which describes Cross-site Scripting flaws, and can be mapped to ATT&CK technique T1190 for exploiting vulnerabilities in web applications, emphasizing the need for both immediate patching and ongoing security monitoring to protect against exploitation attempts.