CVE-2015-2840 in Netscaler
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in help/rt/large_search.html in Citrix NetScaler before 10.5 build 52.3nc allows remote attackers to inject arbitrary web script or HTML via the searchQuery parameter.
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Analysis
by VulDB Data Team • 05/02/2022
The vulnerability identified as CVE-2015-2840 represents a critical cross-site scripting flaw within Citrix NetScaler's web interface, specifically in the help/rt/large_search.html component. This issue affects Citrix NetScaler appliances running versions prior to 10.5 build 52.3nc, creating a significant security risk for organizations relying on these network delivery controllers. The vulnerability resides in the improper validation and sanitization of user input within the searchQuery parameter, which is processed in the large_search.html help file that is accessible through the appliance's web management interface.
The technical implementation of this vulnerability stems from the application's failure to properly encode or escape user-supplied input before rendering it within the web page context. When an attacker submits malicious content through the searchQuery parameter, the web application directly incorporates this unvalidated input into the HTML response without adequate sanitization measures. This allows attackers to inject arbitrary JavaScript code or HTML content that executes in the context of other users' browsers who visit the affected help page. The vulnerability specifically targets the web-based management interface of Citrix NetScaler, making it particularly dangerous as it could be exploited by attackers who gain access to the appliance's administrative interface or by malicious actors who discover the vulnerability through reconnaissance activities.
The operational impact of this XSS vulnerability extends beyond simple data theft or defacement, as it enables attackers to potentially escalate privileges and gain unauthorized access to sensitive network infrastructure. Attackers could leverage this vulnerability to steal session cookies, perform actions on behalf of authenticated users, or redirect victims to malicious websites that could further compromise their systems. The vulnerability affects the appliance's help functionality, which is typically accessible to users with administrative privileges, making it a prime target for privilege escalation attacks. According to CWE classification, this represents a CWE-79: Cross-site Scripting vulnerability, which is categorized under the broader category of input validation flaws. The ATT&CK framework would classify this as a technique for "Web Application Exploitation" under the T1190 category, potentially leading to "Exploitation for Privilege Escalation" and "Initial Access" through web-based attack vectors.
Organizations should immediately implement mitigations including updating to Citrix NetScaler version 10.5 build 52.3nc or later, which contains the necessary patches to address this vulnerability. Network administrators should also consider implementing additional security controls such as web application firewalls that can detect and block malicious XSS payloads, disabling unnecessary help functionality where possible, and implementing strict input validation policies for all user-supplied data. The vulnerability demonstrates the critical importance of proper input sanitization in web applications and highlights the need for regular security assessments of network infrastructure components. Organizations should also conduct comprehensive security audits to identify similar vulnerabilities in other components of their Citrix NetScaler deployments and ensure that all administrative interfaces are properly secured with strong authentication mechanisms and access controls.