CVE-2025-7775: Citrix NetScaler ADC RCE Vulnerability

CVE-2025-7775 Overview

CVE-2025-7775 is a critical memory overflow vulnerability affecting Citrix NetScaler ADC and NetScaler Gateway appliances. This vulnerability enables remote code execution (RCE) and/or denial of service (DoS) when NetScaler is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server. The vulnerability also affects load balancing virtual servers of type HTTP, SSL, or HTTP_QUIC when bound with IPv6 services or servicegroups, as well as CR virtual servers with type HDX.

This vulnerability has been added to the CISA Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation in the wild. Organizations using affected NetScaler configurations should prioritize remediation immediately.

Critical Impact

Unauthenticated remote attackers can exploit this memory overflow to achieve full system compromise through remote code execution, or cause service disruption via denial of service attacks on critical network infrastructure components.

Affected Products

• Citrix NetScaler Application Delivery Controller 13.1, 14.1, 13.1-FIPS, and NDcPP editions
• Citrix NetScaler Gateway 13.1 and 14.1
• NetScaler appliances configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy), AAA virtual server, or CR virtual server with HDX type

Discovery Timeline

• August 26, 2025 - CVE-2025-7775 published to NVD
• October 24, 2025 - Last updated in NVD database

Technical Details for CVE-2025-7775

Vulnerability Analysis

CVE-2025-7775 is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which encompasses various memory safety issues including buffer overflows. The vulnerability exists in the memory handling routines of NetScaler ADC and Gateway when processing requests through specific virtual server configurations.

The attack can be executed remotely over the network, though it requires certain preconditions to be met (specific NetScaler configurations must be in place). Once exploited, an attacker can potentially achieve complete compromise of the affected system, including the ability to execute arbitrary code with elevated privileges or render the device unavailable through denial of service.

Given that NetScaler ADC and Gateway appliances often serve as critical network infrastructure components—handling VPN access, application delivery, and authentication services—successful exploitation could provide attackers with a strategic foothold for further network penetration or disruption of essential business services.

Root Cause

The root cause of CVE-2025-7775 is a memory overflow condition (CWE-119) in the request processing logic. When NetScaler appliances are configured with specific virtual server types (Gateway, AAA, or certain LB configurations with IPv6 services), the system fails to properly validate the boundaries of memory operations during request handling. This allows an attacker to write data beyond the intended buffer boundaries, corrupting adjacent memory regions.

Attack Vector

The vulnerability is exploitable over the network without authentication. The attack targets NetScaler appliances configured in the following modes:

1. Gateway Mode: VPN virtual server, ICA Proxy, CVPN, or RDP Proxy configurations
2. AAA Virtual Server: Authentication, Authorization, and Accounting services
3. Load Balancing: HTTP, SSL, or HTTP_QUIC virtual servers bound with IPv6 services or servicegroups
4. Content Routing: CR virtual server with HDX type

An attacker can craft malicious requests that trigger the memory overflow condition, potentially leading to code execution in the context of the NetScaler service or causing the appliance to crash and become unavailable.

The vulnerability mechanism involves improper bounds checking during memory operations within the virtual server request processing pipeline. When specific conditions are met, attacker-controlled data can overflow allocated buffer boundaries. For detailed technical information, refer to the Citrix Knowledge Base Article.

Detection Methods for CVE-2025-7775

Indicators of Compromise

• Unexpected crashes or restarts of NetScaler ADC or Gateway appliances
• Anomalous network traffic patterns to Gateway, AAA, or LB virtual server endpoints
• Unusual process behavior or memory consumption on NetScaler devices
• Evidence of unauthorized code execution in NetScaler system logs

Detection Strategies

• Monitor NetScaler appliance logs for crash dumps, core files, or unexpected service restarts
• Deploy network intrusion detection signatures for anomalous traffic to NetScaler virtual servers
• Implement behavioral analysis to detect memory corruption exploitation attempts
• Review system integrity monitoring alerts for unauthorized modifications to NetScaler binaries or configurations

Monitoring Recommendations

• Enable comprehensive logging on all NetScaler ADC and Gateway appliances
• Configure SIEM correlation rules to detect patterns indicative of exploitation attempts
• Establish baseline metrics for NetScaler performance and alert on anomalies
• Monitor the CISA KEV Catalog for updated threat intelligence related to this vulnerability

How to Mitigate CVE-2025-7775

Immediate Actions Required

• Apply the latest security patches from Citrix immediately to all affected NetScaler ADC and Gateway appliances
• Review NetScaler configurations to identify all instances of vulnerable virtual server types (Gateway, AAA, LB with IPv6, CR with HDX)
• Implement network segmentation to limit exposure of NetScaler management and virtual server interfaces
• Enable enhanced logging and monitoring on all NetScaler appliances to detect potential exploitation attempts

Patch Information

Citrix has released security updates to address this vulnerability. Administrators should consult the Citrix Knowledge Base Article CTX694938 for specific patch versions and upgrade instructions for NetScaler ADC and Gateway appliances. Due to the critical severity and known exploitation status, patching should be prioritized as an emergency remediation activity.

Affected versions include:

• NetScaler ADC and Gateway 13.1 series
• NetScaler ADC and Gateway 14.1 series
• NetScaler ADC 13.1-FIPS edition
• NetScaler ADC NDcPP edition

Workarounds

• If immediate patching is not possible, consider temporarily disabling or restricting access to vulnerable virtual server configurations
• Implement strict IP allowlisting for access to Gateway, AAA, and affected LB virtual servers
• Deploy Web Application Firewall (WAF) rules to filter potentially malicious requests
• Consider isolating affected NetScaler appliances behind additional network security controls until patches can be applied

# Example: Restrict access to Gateway virtual server (temporary mitigation)
# Add ACL to limit source IPs that can access the vulnerable endpoint
add ns acl RESTRICT_CVE_2025_7775 DENY -srcIP != "10.0.0.0-10.255.255.255" -destPort 443 -protocol TCP
apply ns acls

# Note: This is a temporary measure - apply official Citrix patches as soon as possible