CVE-2020-8300 in ADC
Summary
by MITRE • 06/16/2021
Citrix ADC and Citrix/NetScaler Gateway before 13.0-82.41, 12.1-62.23, 11.1-65.20 and Citrix ADC 12.1-FIPS before 12.1-55.238 suffer from improper access control allowing SAML authentication hijack through a phishing attack to steal a valid user session. Note that Citrix ADC or Citrix Gateway must be configured as a SAML SP or a SAML IdP for this to be possible.
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Analysis
by VulDB Data Team • 06/19/2021
Citrix ADC and Citrix Gateway appliances configured as SAML service providers or identity providers are vulnerable to a critical access control flaw that enables attackers to hijack valid user sessions through sophisticated phishing techniques. This vulnerability affects multiple version lines including 13.0-82.41, 12.1-62.23, 11.1-65.20, and the FIPS version 12.1-55.238, representing a significant security gap in enterprise authentication infrastructure. The flaw stems from inadequate validation of SAML authentication flows, creating opportunities for malicious actors to exploit the trust relationship between the identity provider and service provider components.
The technical implementation of this vulnerability resides in the improper handling of SAML assertion processing within the Citrix gateway components. When a user authenticates through a SAML IdP, the system should maintain strict session integrity and validate the authenticity of each assertion received. However, the flawed implementation allows attackers to craft malicious SAML responses that appear legitimate to the Citrix appliance, enabling session hijacking without proper authentication. This weakness directly maps to CWE-285: Improper Authorization and aligns with ATT&CK technique T1566.002: Phishing for Information, as it leverages social engineering to deliver malicious authentication tokens.
The operational impact of this vulnerability extends beyond simple session theft, as successful exploitation can lead to complete administrative access to protected networks and resources. Attackers can leverage this flaw to bypass multi-factor authentication mechanisms, access sensitive data, and move laterally within the network. The vulnerability is particularly dangerous because it requires minimal user interaction beyond initial phishing delivery, making it difficult to detect through traditional monitoring approaches. Organizations with Citrix appliances configured as SAML endpoints face elevated risk of data breaches and unauthorized access, especially in environments where these appliances serve as primary authentication gateways.
Mitigation strategies should prioritize immediate patching of affected Citrix versions to address the root cause of the access control failure. Organizations must also implement enhanced monitoring for unusual SAML assertion patterns and establish network segmentation to limit the impact of potential exploitation. Additional defensive measures include implementing strict certificate validation for SAML communications, deploying application-level firewalls to filter malicious SAML responses, and conducting regular security assessments of authentication infrastructure. The remediation process should also include comprehensive user education about phishing attack recognition and establishing incident response procedures specifically tailored to SAML-based authentication compromises.