CVE-2016-11086 in oauth-ruby gem
Summary
by MITRE
lib/oauth/consumer.rb in the oauth-ruby gem through 0.5.4 for Ruby does not verify server X.509 certificates if a certificate bundle cannot be found, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information.
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Analysis
by VulDB Data Team • 04/21/2023
The vulnerability identified as CVE-2016-11086 resides within the oauth-ruby gem version 0.5.4 and earlier, specifically in the lib/oauth/consumer.rb file. This flaw represents a critical security oversight in the gem's certificate validation mechanism that fundamentally undermines the security of SSL/TLS connections used for OAuth authentication processes. The vulnerability occurs when the gem fails to properly validate X.509 certificates during the OAuth communication process, creating a significant attack surface that adversaries can exploit to compromise sensitive authentication flows.
The technical flaw stems from the gem's improper handling of certificate verification when the required certificate bundle files are unavailable or cannot be located on the system. When the oauth-ruby gem attempts to establish a secure connection to an OAuth server, it should validate the server's X.509 certificate against a trusted certificate authority to ensure the authenticity of the endpoint. However, in the affected versions, if the gem cannot locate or access the certificate bundle, it silently disables certificate verification entirely rather than failing securely. This behavior creates a dangerous fallback mechanism where the system operates in an insecure state without alerting administrators or users to the compromised security posture.
The operational impact of this vulnerability is severe and multifaceted, as it enables man-in-the-middle attacks that can completely bypass the security mechanisms designed to protect OAuth authentication. Attackers can exploit this weakness by positioning themselves between the client application and the OAuth server, intercepting and modifying communication without detection. This allows them to impersonate legitimate servers, capture authentication tokens, and potentially gain unauthorized access to protected resources. The vulnerability affects any application using the oauth-ruby gem for OAuth authentication, making it particularly dangerous in environments where sensitive data is transmitted through OAuth protocols, including financial services, healthcare applications, and enterprise authentication systems.
This vulnerability aligns with CWE-295, which addresses "Improper Certificate Validation," and represents a classic example of insecure cryptographic implementation. The flaw also maps to ATT&CK technique T1566.001, "Phishing via Service Provider", where attackers can exploit the insecure OAuth implementation to conduct phishing attacks by spoofing legitimate service providers. Additionally, the vulnerability demonstrates characteristics of T1071.004, "Application Layer Protocol: DNS," as the compromised authentication process can be leveraged to redirect users to malicious endpoints. Organizations using the affected gem are particularly vulnerable to credential theft, session hijacking, and data exfiltration attacks that can compromise entire authentication ecosystems.
The recommended mitigations include immediate upgrading to a patched version of the oauth-ruby gem where certificate validation is properly enforced even when certificate bundles are unavailable. System administrators should also implement certificate pinning mechanisms where possible, configure explicit certificate bundle paths, and monitor for unauthorized certificate changes in their environments. Organizations should conduct comprehensive vulnerability assessments to identify all applications using the affected gem and implement proper security monitoring to detect potential exploitation attempts. Additionally, implementing network-level security controls such as SSL/TLS inspection and certificate transparency monitoring can provide additional layers of protection against this specific attack vector.