CVE-2016-9814 in SimpleSAMLphp
Summary
by MITRE
The validateSignature method in the SAML2\Utils class in SimpleSAMLphp before 1.14.10 and simplesamlphp/saml2 library before 1.9.1, 1.10.x before 1.10.3, and 2.x before 2.3.3 allows remote attackers to spoof SAML responses or possibly cause a denial of service (memory consumption) by leveraging improper conversion of return values to boolean.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 09/02/2020
The vulnerability identified as CVE-2016-9814 represents a critical security flaw in SimpleSAMLphp authentication systems that affects multiple versions of the software library. This issue resides within the SAML2\Utils class where the validateSignature method fails to properly handle return value conversions to boolean types, creating a pathway for malicious actors to exploit the authentication mechanism. The vulnerability impacts organizations relying on SAML-based single sign-on implementations where SimpleSAMLphp serves as the identity provider or service provider component.
The technical root cause stems from improper handling of boolean conversion in the signature validation process, specifically within the validateSignature method of the SAML2\Utils class. When cryptographic signatures are validated, the method returns a value that should be properly interpreted as a boolean result indicating success or failure of the signature verification. However, due to flawed type conversion logic, attackers can manipulate the return values to bypass signature validation entirely. This improper conversion creates a condition where maliciously crafted SAML responses can appear legitimate to the validation system, allowing unauthorized parties to forge authentication tokens and gain unauthorized access to protected resources.
The operational impact of this vulnerability extends beyond simple authentication bypass to potentially enable denial of service conditions through memory consumption attacks. Attackers exploiting this flaw can craft SAML responses that cause the authentication system to consume excessive memory resources during signature validation, leading to system resource exhaustion and potential service disruption. The vulnerability affects multiple release branches including versions before 1.14.10 of SimpleSAMLphp and various versions of the simplesamlphp/saml2 library across different major versions, indicating a widespread exposure across organizations using these authentication frameworks.
This vulnerability aligns with CWE-697, which addresses incorrect boolean evaluation in software systems, and represents a classic case of improper input validation that can lead to authentication bypass. The attack vector leverages the principle of least privilege by allowing remote attackers to manipulate the authentication flow without requiring local system access or elevated privileges. From an attacker perspective, this vulnerability maps to ATT&CK technique T1566.001 for initial access through valid accounts and potentially T1499.004 for denial of service through resource exhaustion. Organizations implementing SAML-based authentication using affected SimpleSAMLphp versions face significant risk of unauthorized access to sensitive systems and data, particularly in environments where SAML responses are processed without additional validation layers.
The recommended mitigation strategy involves immediate upgrade to patched versions of SimpleSAMLphp and the simplesamlphp/saml2 library, specifically versions 1.14.10 and later for the main library, and 1.9.1, 1.10.3, and 2.3.3 for the respective library versions. Organizations should also implement additional monitoring for suspicious authentication patterns and consider deploying network segmentation to limit exposure of authentication systems. Security teams should conduct comprehensive vulnerability assessments across all systems using affected software versions and ensure proper patch management processes are in place to prevent similar issues in the future.