CVE-2016-4945 in Netscaler Gateway
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in vpn/js/gateway_login_form_view.js in Citrix NetScaler Gateway 11.0 before Build 66.11 allows remote attackers to inject arbitrary web script or HTML via the NSC_TMAC cookie.
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Analysis
by VulDB Data Team • 09/29/2024
The vulnerability identified as CVE-2016-4945 represents a critical cross-site scripting flaw within Citrix NetScaler Gateway 11.0 software before build 66.11. This security weakness resides in the vpn/js/gateway_login_form_view.js JavaScript file and specifically targets the handling of the NSC_TMAC cookie parameter. The flaw enables remote attackers to execute malicious web scripts or HTML code within the context of a victim's browser session, potentially compromising user data and system integrity.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the JavaScript component responsible for rendering the gateway login form. When the NSC_TMAC cookie value is processed by the gateway_login_form_view.js script, the application fails to properly sanitize or escape the cookie data before incorporating it into dynamic HTML content. This inadequate sanitization creates an opening for attackers to inject malicious payloads that can be executed when the page renders, particularly during authentication processes where users interact with the login interface.
The operational impact of this vulnerability extends beyond simple script injection, as it provides attackers with potential access to sensitive user sessions and authentication tokens within the Citrix NetScaler environment. An attacker could exploit this flaw to steal user credentials, hijack sessions, or redirect users to malicious websites. The vulnerability is particularly concerning in enterprise environments where Citrix NetScaler Gateways serve as critical access points for remote workers, potentially allowing unauthorized access to corporate networks and sensitive resources. The attack vector requires minimal privileges since it operates over standard web protocols and can be executed through simple cookie manipulation techniques.
Mitigation strategies for this vulnerability should include immediate application of Citrix's security patches and updates, specifically targeting build 66.11 or later versions that address the XSS flaw in the gateway_login_form_view.js component. Organizations should also implement robust input validation mechanisms and output encoding practices throughout their web applications to prevent similar issues. Security measures should include monitoring for suspicious cookie values and implementing Content Security Policy headers to limit script execution capabilities. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and maps to ATT&CK technique T1566 for social engineering via malicious web content, emphasizing the need for comprehensive web application security controls and regular vulnerability assessments to prevent exploitation of such critical flaws in enterprise security infrastructure.