CVE-2016-5697 in Ruby-saml
Summary
by MITRE
Ruby-saml before 1.3.0 allows attackers to perform XML signature wrapping attacks via unspecified vectors.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2016-5697 affects ruby-saml versions prior to 1.3.0 and represents a critical security flaw that enables attackers to execute XML signature wrapping attacks. This vulnerability resides within the SAML (Security Assertion Markup Language) implementation within the ruby-saml gem, which is commonly used for implementing SAML-based single sign-on (SSO) solutions in Ruby applications. The issue stems from insufficient validation of XML signatures, creating a pathway for malicious actors to manipulate SAML assertions by wrapping or embedding additional XML content within the signature structure.
The technical flaw manifests when the ruby-saml library fails to properly verify the integrity of XML signatures during SAML assertion processing. Attackers can exploit this weakness by crafting malicious SAML responses that contain wrapped signatures, allowing them to bypass authentication mechanisms and potentially gain unauthorized access to protected resources. This vulnerability specifically affects the XML signature validation process where the library does not adequately check for signature wrapping techniques that can cause the signature to validate against unintended content. The issue falls under CWE-347, which addresses improper verification of cryptographic signatures, and aligns with ATT&CK technique T1550.001 for use of valid credentials through legitimate authentication protocols.
The operational impact of CVE-2016-5697 is significant for organizations relying on ruby-saml for SAML-based authentication systems. Attackers exploiting this vulnerability can manipulate SAML assertions to impersonate legitimate users, access restricted resources, or escalate privileges within the authenticated system. The attack vector is particularly concerning because it can be executed without requiring knowledge of the underlying cryptographic keys, making it difficult to detect and prevent through traditional key management practices. Systems using ruby-saml versions before 1.3.0 are vulnerable to man-in-the-middle attacks where attackers can intercept and modify SAML responses, potentially compromising entire authentication chains and user sessions.
Organizations should immediately upgrade their ruby-saml gem to version 1.3.0 or later to address this vulnerability. Additional mitigations include implementing proper XML signature validation controls, monitoring SAML assertion processing for anomalous behavior, and ensuring that all SAML endpoints properly validate signature integrity. Security teams should also consider implementing network-level protections such as signature validation firewalls and regular security scanning of SAML implementations. The vulnerability demonstrates the critical importance of proper XML security practices in authentication systems and highlights the need for regular security updates and vulnerability assessments in identity management solutions. Organizations using ruby-saml should also review their SAML configuration to ensure that signature validation is properly enforced and that no bypass mechanisms exist within their authentication flows.