CVE-2018-6811 in NetScaler ADC
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in Citrix NetScaler ADC 10.5, 11.0, 11.1, and 12.0, and NetScaler Gateway 10.5, 11.0, 11.1, and 12.0 allow remote attackers to inject arbitrary web script or HTML via the Citrix NetScaler interface.
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Analysis
by VulDB Data Team • 02/17/2023
The vulnerability identified as CVE-2018-6811 represents a critical cross-site scripting weakness affecting Citrix NetScaler ADC and Gateway products across multiple versions including 10.5, 11.0, 11.1, and 12.0. This flaw exists within the web administration interfaces of these network security appliances, creating a significant attack surface that enables remote exploitation without authentication requirements. The vulnerability stems from insufficient input validation and output encoding mechanisms within the Citrix management consoles, allowing malicious actors to inject malicious scripts that execute in the context of authenticated users' browsers.
The technical implementation of this vulnerability involves the improper sanitization of user-supplied input parameters within the web interface components of Citrix NetScaler appliances. Attackers can leverage this weakness by crafting malicious payloads that are then processed and rendered by the vulnerable web interface, leading to script execution in the victim's browser context. This occurs because the system fails to properly encode or escape special characters in user-provided data before displaying it within web pages, creating conditions where attacker-controlled input can be interpreted as executable code rather than plain text.
From an operational impact perspective, this vulnerability poses severe risks to organizations relying on Citrix NetScaler appliances for network security and application delivery. Remote attackers can exploit these XSS flaws to steal session cookies, perform unauthorized administrative actions, redirect users to malicious sites, or extract sensitive information from the appliance's management interface. The implications extend beyond simple script injection as attackers can potentially escalate privileges, gain persistent access to the appliance, and use it as a pivot point for further attacks within the network infrastructure.
The attack vectors for CVE-2018-6811 align with the ATT&CK framework's initial access and persistence phases, specifically targeting the web application attack surface and leveraging the compromised management interface for ongoing access. Organizations using affected Citrix versions face potential compromise of their entire network security posture, as these appliances often serve as critical gateways for application delivery and security enforcement. The vulnerability's classification under CWE-79 indicates improper neutralization of input during web page generation, making it a classic example of web application security flaws that can lead to complete system compromise.
Mitigation strategies for this vulnerability require immediate patching of affected Citrix NetScaler versions through official security updates provided by Citrix. Organizations should also implement network segmentation to limit access to management interfaces, deploy web application firewalls to detect and block malicious payloads, and establish monitoring for suspicious activities in appliance logs. Additionally, organizations should conduct comprehensive security assessments of their Citrix appliance configurations, disable unnecessary web interface features, and implement multi-factor authentication for administrative access to reduce the attack surface and prevent exploitation of this vulnerability.