CVE-2017-6316 in Netscaler SD-WAN
Summary
by MITRE
Citrix NetScaler SD-WAN devices through v9.1.2.26.561201 allow remote attackers to execute arbitrary shell commands as root via a CGISESSID cookie. On CloudBridge (the former name of NetScaler SD-WAN) devices, the cookie name was CAKEPHP rather than CGISESSID.
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Analysis
by VulDB Data Team • 02/05/2025
This vulnerability represents a critical remote code execution flaw in Citrix NetScaler SD-WAN appliances that affects versions up to v9.1.2.26.561201. The vulnerability stems from improper input validation within the web administration interface where the system fails to properly sanitize user-supplied data in the CGISESSID cookie parameter. This weakness allows remote attackers to inject malicious shell commands that execute with root privileges on the underlying operating system. The flaw exists due to insufficient validation of cookie values before they are processed by the web server, creating an exploitation vector that bypasses normal authentication mechanisms and directly targets the system's command execution capabilities.
The technical implementation of this vulnerability leverages a classic command injection attack pattern where the malicious payload is embedded within the cookie value and subsequently passed to shell execution functions without proper sanitization. Attackers can craft specially formatted cookie values containing shell commands that get executed by the system's underlying shell processes. The vulnerability affects both the standard NetScaler SD-WAN devices and CloudBridge appliances, with the latter using a different cookie name CAKEPHP instead of CGISESSID, but maintaining the same underlying security flaw. This indicates a systemic issue in the web application's input handling across different product variants, suggesting that similar vulnerabilities may exist in other cookie handling mechanisms within the same codebase.
The operational impact of this vulnerability is severe and potentially catastrophic for organizations relying on Citrix NetScaler SD-WAN infrastructure. Remote attackers can gain complete system compromise with root privileges, enabling them to access all network resources managed by the appliance, extract sensitive configuration data, modify network policies, and potentially use the compromised device as a pivot point for further attacks within the network. The vulnerability eliminates the need for any authentication credentials to achieve system-level access, making it particularly dangerous as it can be exploited from any location on the internet without requiring prior access to the network. This aligns with ATT&CK technique T1059.001 for command and scripting interpreter and CWE-78 for improper neutralization of special elements used in OS commands, highlighting the fundamental flaw in how the system processes user-supplied input.
Organizations should implement immediate mitigations including applying the vendor-provided security patches, disabling unnecessary web administration interfaces, implementing network segmentation to restrict access to the affected appliances, and monitoring network traffic for suspicious cookie values. Additional protective measures include deploying web application firewalls to detect and block malicious cookie content, implementing strict access controls to limit administrative access to trusted networks, and conducting thorough network audits to identify any potential compromise. The vulnerability demonstrates the critical importance of input validation and proper sanitization of all user-supplied data in web applications, particularly in administrative interfaces that execute system commands. Organizations should also consider implementing continuous security monitoring and vulnerability assessment programs to identify similar flaws in other network infrastructure components, as this vulnerability represents a common pattern that may exist in other products within the Citrix ecosystem or similar vendor solutions.