CVE-2023-4966: Citrix NetScaler ADC Info Disclosure Flaw

CVE-2023-4966 Overview

Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA  virtual server.

Critical Impact

This vulnerability can lead to unauthorized disclosure of sensitive session data.

Affected Products

• citrix netscaler_application_delivery_controller
• citrix netscaler_gateway

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to citrix
• Not Available - CVE CVE-2023-4966 assigned
• Not Available - citrix releases security patch
• 2023-10-10 - CVE CVE-2023-4966 published to NVD
• 2025-10-24 - Last updated in NVD database

Technical Details for CVE-2023-4966

Vulnerability Analysis

The CVE-2023-4966 vulnerability is categorized as an information disclosure flaw, specifically triggered when the affected systems are configured as Gateway or AAA virtual servers. Attackers can exploit this vulnerability over the network due to its low complexity.

Root Cause

The root cause lies in improper handling of session tokens, which can be leaked due to incorrect permissions or misconfigurations within Citrix's NetScaler ADC and Gateway products.

Attack Vector

The vulnerability can be exploited remotely over a network with no authentication required.

# Hypothetical exploitation code
import requests

url = "https://vulnerable-server.example.com/vpn/index.html"
response = requests.get(url, verify=False)
if "SESSION_TOKEN" in response.text:
    print("Session token disclosed!")

Detection Methods for CVE-2023-4966

Indicators of Compromise

• Unexpected session token disclosures in logs
• Anomalous access attempts from unrecognized IP addresses
• Increased volume of data traffic without associated session activity

Detection Strategies

Leverage SentinelOne's behavioral AI to monitor for unusual data patterns and access attempts that may indicate exploitation. Configuring alerts for traffic anomalies targeting Citrix Gateway endpoints can be effective.

Monitoring Recommendations

Regularly audit access logs for unauthorized access attempts and monitor for unusual outbound connections from servers running Citrix NetScaler.

How to Mitigate CVE-2023-4966

Immediate Actions Required

• Disable vulnerable configurations temporarily
• Enhance monitoring on affected systems
• Inform stakeholders about potential data risks

Patch Information

Apply the security patches provided by Citrix as per their advisory CTX579459.

Workarounds

Restrict network access to only trusted IPs and implement additional authentication layers where feasible.

# Example configuration to mitigate
iptables -A INPUT -p tcp --dport 443 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP