CVE-2018-3769 in ruby-grape Gem
Summary
by MITRE
ruby-grape ruby gem suffers from a cross-site scripting (XSS) vulnerability via "format" parameter.
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Analysis
by VulDB Data Team • 04/03/2023
The CVE-2018-3769 vulnerability represents a critical cross-site scripting flaw discovered in the ruby-grape gem, a popular framework for building RESTful APIs in ruby applications. This vulnerability specifically manifests through improper handling of the "format" parameter, which is commonly used to specify response formats such as json, xml, or html within api endpoints. The flaw allows malicious actors to inject arbitrary javascript code into responses that are then executed in the context of other users' browsers when they interact with the vulnerable application. This type of vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as one of the most prevalent and dangerous web application security flaws according to the CWE database. The vulnerability demonstrates a classic failure in input sanitization where user-supplied data is directly incorporated into web responses without proper encoding or validation.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious payload containing javascript code within the format parameter of a grape api endpoint. When the application processes this request and returns a response that includes the unsanitized format parameter value, the injected javascript executes in the victim's browser context. This can lead to session hijacking, credential theft, or redirection to malicious sites. The vulnerability is particularly concerning because grape is widely used in enterprise applications and web services, making it a prime target for attackers seeking to compromise large user bases. The flaw essentially allows an attacker to bypass normal security boundaries and execute arbitrary code in the context of authenticated users, potentially leading to full system compromise.
The operational impact of CVE-2018-3769 extends beyond simple script execution as it can enable sophisticated attack chains that leverage the compromised user sessions. Attackers can exploit this vulnerability to perform actions such as modifying user data, accessing sensitive information, or even escalating privileges within the application. The vulnerability is particularly dangerous in environments where the grape framework handles authentication tokens or sensitive data processing, as it could allow attackers to gain unauthorized access to protected resources. Organizations using ruby-grape applications may experience significant security breaches including data exfiltration, service disruption, and compliance violations, especially in regulated industries where user privacy and data protection are paramount. The attack surface is broad since the vulnerability affects any application that uses the grape gem and fails to properly validate the format parameter input.
Mitigation strategies for CVE-2018-3769 require immediate patching of the ruby-grape gem to version 1.2.4 or later, which includes proper input sanitization for the format parameter. Organizations should also implement comprehensive input validation at multiple layers including application-level filtering, web application firewalls, and output encoding for all user-supplied data. Security teams should conduct thorough vulnerability assessments of all ruby applications using grape to identify potential exposure points and ensure proper parameter handling. The remediation process should include code reviews focused on input validation practices and implementation of secure coding guidelines that align with OWASP Top Ten recommendations. Additionally, organizations should consider implementing content security policies and monitoring for suspicious parameter values to detect potential exploitation attempts. The vulnerability highlights the importance of keeping all third-party libraries updated and demonstrates the critical need for proper input sanitization in web applications, particularly those handling user-provided data through api endpoints.