CVE-2018-7340 in Network Gateway
Summary
by MITRE
Duo Network Gateway 1.2.9 and earlier may incorrectly utilize the results of XML DOM traversal and canonicalization APIs in such a way that an attacker may be able to manipulate the SAML data without invalidating the cryptographic signature, allowing the attack to potentially bypass authentication to SAML service providers.
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Analysis
by VulDB Data Team • 08/29/2023
The vulnerability identified as CVE-2018-7340 affects the Duo Network Gateway version 1.2.9 and earlier, presenting a critical security flaw in the handling of SAML (Security Assertion Markup Language) authentication workflows. This issue stems from improper implementation of XML DOM traversal and canonicalization APIs within the gateway's processing logic, creating a fundamental weakness that undermines the integrity of SAML assertions.
The technical flaw manifests when the Duo Network Gateway processes SAML responses from identity providers. During the XML processing phase, the system fails to properly validate or sanitize the XML structure before performing canonicalization operations. This improper handling allows attackers to manipulate the SAML data elements while maintaining the cryptographic signature validity, effectively creating a signature wrapping attack vector. The vulnerability specifically targets the XML canonicalization process which is designed to ensure consistent XML representation for cryptographic signing, but the flawed implementation enables attackers to rearrange or modify XML elements without breaking the signature verification.
From an operational impact perspective, this vulnerability compromises the core authentication mechanism of SAML-based single sign-on systems. An attacker who successfully exploits this flaw can manipulate SAML assertions to gain unauthorized access to protected services, potentially escalating privileges or accessing restricted resources. The attack vector is particularly dangerous because it operates silently, allowing the manipulation to bypass traditional signature validation checks that should prevent tampered SAML responses from being accepted by service providers. This creates a false sense of security where legitimate authentication flows appear intact while unauthorized access is granted.
The vulnerability aligns with CWE-347, which addresses improper verification of cryptographic signatures, and relates to ATT&CK technique T1550.001 for legitimate credentials, as it enables unauthorized access through manipulated authentication tokens. Organizations relying on Duo Network Gateway for SAML authentication face significant risk of credential compromise and unauthorized system access. The attack requires minimal privileges and can be executed against any SAML service provider that accepts assertions from the vulnerable gateway, making it particularly dangerous in enterprise environments where multiple services depend on centralized authentication.
Mitigation strategies should focus on immediate patching to version 1.2.10 or later, which addresses the XML canonicalization implementation issues. Organizations should also implement additional monitoring for anomalous SAML assertion patterns and consider implementing signature validation checks beyond the standard gateway mechanisms. Network segmentation and access controls should be reinforced to limit the impact of potential exploitation. Regular security assessments of SAML implementations and XML processing libraries are essential to identify similar vulnerabilities in other authentication systems that may be susceptible to the same class of canonicalization flaws.