CVE-2015-7997 in Netscaler Application Delivery Controller
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in the Nitro API in Citrix NetScaler Application Delivery Controller (ADC) and NetScaler Gateway before 10.1 Build 133.9, 10.5 before Build 58.11, and 10.5.e before Build 56.1505.e on NetScaler Service Delivery Appliance Service VM (SVM) devices allow remote attackers to inject arbitrary web script or HTML via unspecified vectors.
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Analysis
by VulDB Data Team • 05/17/2018
The vulnerability CVE-2015-7997 represents a critical cross-site scripting flaw within the Nitro API component of Citrix NetScaler ADC and Gateway products. This vulnerability affects multiple versions including older releases before specific build numbers and newer versions with their respective build constraints. The flaw exists in the Nitro API implementation which serves as the management interface for configuring and managing NetScaler appliances. The affected systems include both traditional NetScaler ADC appliances and NetScaler Service Delivery Appliance Service VM devices, making this a widespread concern across Citrix deployment environments.
The technical nature of this vulnerability stems from insufficient input validation and output encoding within the Nitro API processing mechanisms. Attackers can exploit this weakness by sending malicious payloads through unspecified vectors that ultimately get executed in the context of authenticated users' browsers. The vulnerability allows remote attackers to inject arbitrary web scripts or HTML code into the application interface, which then executes when legitimate users access the affected management pages. This represents a classic XSS flaw categorized under CWE-79, which specifically addresses cross-site scripting vulnerabilities where untrusted data is improperly sanitized before being rendered in web browsers. The attack vector operates without requiring authentication for the initial injection, making it particularly dangerous as it can be exploited by unauthorized parties.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform session hijacking, steal sensitive configuration data, and potentially escalate privileges within the NetScaler environment. Since the Nitro API provides administrative access to critical network infrastructure components, successful exploitation could lead to complete compromise of the appliance and potentially the entire network segment it protects. The vulnerability affects both the NetScaler ADC and Gateway products, which are commonly deployed as critical network security devices handling traffic control, load balancing, and SSL termination functions. Organizations using these appliances may face significant risks including data exfiltration, service disruption, and unauthorized access to backend systems that rely on NetScaler for traffic management.
Mitigation strategies should focus on immediate patch application to the affected versions, with particular attention to the specific build numbers mentioned in the vulnerability description. Organizations should implement network segmentation to limit access to the Nitro API endpoints and consider disabling the API entirely if it's not required for operational purposes. Additional protective measures include implementing web application firewalls to detect and block malicious payloads, conducting regular security assessments of NetScaler configurations, and monitoring for anomalous API access patterns. The vulnerability also aligns with ATT&CK technique T1059.007 which covers "Command and Scripting Interpreter: PowerShell" and T1566 which addresses "Phishing" as attackers could leverage the XSS to deliver additional malicious payloads through compromised user sessions. Network administrators should also consider implementing strict access controls and privilege separation to minimize the potential impact should the vulnerability be successfully exploited.