CVE-2015-20108 in ruby-saml Gem
Summary
by MITRE • 05/27/2023
xml_security.rb in the ruby-saml gem before 1.0.0 for Ruby allows XPath injection and code execution because prepared statements are not used.
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Analysis
by VulDB Data Team • 07/14/2025
The vulnerability identified as CVE-2015-20108 affects the ruby-saml gem version 1.0.0 and earlier, specifically within the xml_security.rb component. This security flaw represents a critical weakness in the gem's handling of XML security operations that can lead to severe consequences including unauthorized access and arbitrary code execution. The vulnerability stems from improper implementation of XML processing mechanisms that fail to properly sanitize user input before incorporating it into XML queries or processing statements. The ruby-saml gem is commonly used in Ruby applications to implement Security Assertion Markup Language SAML protocols for single sign-on functionality, making this vulnerability particularly concerning for organizations relying on SAML-based authentication systems.
The technical root cause of this vulnerability lies in the absence of proper prepared statements or parameterized queries when processing XML data within the xml_security.rb file. This implementation flaw allows attackers to inject malicious XPath expressions through crafted XML inputs that are then processed without adequate sanitization or validation. When the application processes XML documents containing specially crafted XPath expressions, the lack of prepared statements creates an environment where attacker-controlled input can be directly interpreted as part of the XPath query logic. This behavior directly aligns with CWE-649, which specifically addresses weaknesses related to the use of weak or improperly implemented XPath queries that can lead to injection attacks. The vulnerability creates a direct pathway for attackers to manipulate XML processing operations and potentially extract sensitive information or execute arbitrary code within the context of the application.
The operational impact of CVE-2015-20108 extends beyond simple data extraction to encompass full system compromise potential. An attacker exploiting this vulnerability could gain unauthorized access to sensitive authentication data, potentially bypassing SAML-based authentication mechanisms entirely. The vulnerability's ability to enable code execution through XPath injection means that malicious actors could manipulate the application's behavior to perform actions beyond simple data retrieval. This could result in unauthorized user account access, data breaches, or even complete system compromise depending on the application's privileges and the nature of the SAML implementation. Organizations using ruby-saml versions prior to 1.0.0 face significant risk exposure, particularly those implementing SAML-based authentication systems where the vulnerability could be leveraged to undermine the entire authentication infrastructure. The attack surface is further expanded by the fact that many applications using ruby-saml may not properly validate or sanitize XML inputs from external sources, creating additional attack vectors.
Mitigation strategies for this vulnerability center around immediate remediation through version updates to ruby-saml 1.0.0 or later, which contain the necessary fixes for the XPath injection issues. Security teams should conduct comprehensive assessments of all systems utilizing ruby-saml to identify potential exposure and implement proper input validation and sanitization measures. The fix typically involves implementing proper prepared statements or parameterized queries when processing XML data, ensuring that user-controlled inputs are properly escaped or encoded before being incorporated into XPath expressions. Organizations should also consider implementing network-level protections such as web application firewalls and monitoring for suspicious XML processing patterns. From a defense-in-depth perspective, implementing proper access controls and limiting the privileges of applications using ruby-saml can help minimize the potential impact of successful exploitation attempts. The vulnerability's classification under ATT&CK technique T1059.007, which covers command and script injection, indicates that exploitation could enable attackers to execute arbitrary commands on the affected system, further emphasizing the critical nature of immediate remediation. Additionally, organizations should review their overall XML processing security practices and ensure that similar vulnerabilities are not present in other components of their authentication infrastructure.