CVE-2025-5777: Citrix NetScaler ADC Buffer Overflow Flaw

CVE-2025-5777 Overview

Insufficient input validation leading to memory overread when the NetScaler is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server.

Critical Impact

This vulnerability is being actively exploited in the wild and can lead to unauthorized data access.

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-2025-5777 assigned
• Not Available - Citrix releases security patch
• 2025-06-17 - CVE CVE-2025-5777 published to NVD
• 2025-10-30 - Last updated in NVD database

Technical Details for CVE-2025-5777

Vulnerability Analysis

The vulnerability arises due to insufficient input validation on network-facing components of Citrix NetScaler devices. This flaw allows memory overreads, potentially exposing sensitive data.

Root Cause

The issue involves improper checks on input data, leading to an out-of-bounds read scenario.

Attack Vector

Network-based exploitation is possible as the vulnerability affects the Gateway functionality of the device.

// Example exploitation code (sanitized)
#include <stdio.h>
#include <string.h>

int main() {
    char buffer[10];
    // Vulnerable operation
    strcpy(buffer, "This is a test string");
    printf("Buffer: %s\n", buffer);
    return 0;
}

Detection Methods for CVE-2025-5777

Indicators of Compromise

• Unusual outbound traffic patterns
• Access to sensitive memory regions
• Unauthorized data access logs

Detection Strategies

Network traffic analysis systems can identify exploit attempts by spotting irregular data requests or malformed packets targeting known NetScaler vulnerabilities.

Monitoring Recommendations

Implement continuous monitoring on NetScaler devices using SentinelOne’s detection capabilities, which provide real-time alerts to anomalies in network behavior.

How to Mitigate CVE-2025-5777

Immediate Actions Required

• Apply the latest security updates provided by Citrix
• Implement network segmentation to limit exposure
• Deploy intrusion detection systems to monitor for exploitation attempts

Patch Information

Citrix has released security patches available in advisory CTX693420. Deploy these patches promptly to secure affected systems.

Workarounds

Consider disabling vulnerable components if patching is not immediately feasible and ensure robust network policies to limit unauthorized access.

# Configuration example
iptables -A INPUT -p tcp --dport 443 -j DROP