CVE-2025-7775 is a critical memory overflow vulnerability classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) affecting Citrix NetScaler ADC and NetScaler Gateway products. This vulnerability arises when NetScaler is configured in specific modes such as Gateway (including VPN virtual server, ICA Proxy, CVPN, RDP Proxy), AAA virtual server, or when load balancing (LB) virtual servers of types HTTP, SSL, or HTTP_QUIC are bound with IPv6 services or service groups, including DBS IPv6 services or DBS IPv6 servers. Additionally, CR virtual servers of type HDX are also affected. The flaw allows an attacker to trigger a memory overflow condition, which can lead to remote code execution (RCE) or denial of service (DoS) without requiring authentication or user interaction. The vulnerability affects multiple versions of NetScaler ADC and Gateway, including 12.1 FIPS and NDcPP, 13.1, 13.1 FIPS and NDcPP, and 14.1. The CVSS 4.0 base score is 9.2, indicating a critical severity level. The attack vector is network-based, but the complexity is high, and partial attack prerequisites exist, though no privileges or user interaction are required. The vulnerability impacts confidentiality, integrity, and availability with high scope and impact. Although no known exploits are currently reported in the wild, the potential for exploitation is significant given the criticality and the nature of the affected systems, which are widely used for secure remote access and application delivery. The vulnerability stems from improper bounds checking in memory operations, allowing attackers to overflow buffers and execute arbitrary code or disrupt service availability remotely.

For European organizations, the impact of CVE-2025-7775 is substantial due to the widespread use of Citrix NetScaler ADC and Gateway products in enterprise environments for secure remote access, VPN services, application delivery, and load balancing. Exploitation could lead to unauthorized remote code execution, allowing attackers to gain control over critical network infrastructure components, potentially leading to data breaches, lateral movement within networks, and disruption of business-critical services. Denial of service conditions could degrade or completely halt access to essential applications, impacting operational continuity. Given the critical role of these devices in secure communications and access management, exploitation could compromise confidentiality, integrity, and availability of sensitive data and services. This is particularly concerning for sectors such as finance, healthcare, government, and critical infrastructure in Europe, where secure remote access and application delivery are paramount. The lack of required authentication or user interaction lowers the barrier for attackers, increasing the risk of widespread exploitation if patches or mitigations are not promptly applied.

European organizations should prioritize immediate assessment and remediation of this vulnerability. Specific mitigation steps include: 1) Conducting a comprehensive inventory of all NetScaler ADC and Gateway devices to identify affected versions and configurations, especially those using Gateway modes, AAA virtual servers, and load balancing with IPv6 services. 2) Applying vendor-provided patches or updates as soon as they become available; if patches are not yet released, implement temporary mitigations such as disabling or restricting vulnerable virtual server types or IPv6 bindings where feasible. 3) Implementing strict network segmentation and access controls to limit exposure of NetScaler devices to untrusted networks, reducing the attack surface. 4) Monitoring network traffic and device logs for unusual activity indicative of exploitation attempts, including anomalous memory usage or crashes. 5) Employing intrusion detection and prevention systems with updated signatures targeting this vulnerability. 6) Reviewing and hardening configurations related to VPN, ICA Proxy, RDP Proxy, and HDX services to minimize unnecessary exposure. 7) Ensuring robust incident response plans are in place to quickly address potential exploitation. These measures go beyond generic advice by focusing on configuration-specific risk reduction and proactive monitoring tailored to the affected NetScaler functionalities.