CVE-2025-7775 is a critical vulnerability classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) affecting Citrix NetScaler ADC and NetScaler Gateway appliances. The vulnerability manifests as a memory overflow condition that can be triggered remotely, leading to potential remote code execution (RCE) or denial of service (DoS). The affected products include NetScaler ADC and Gateway versions 12.1 FIPS/NDcPP, 13.1, 13.1 FIPS/NDcPP, and 14.1. The flaw specifically arises when NetScaler is configured as a Gateway virtual server (including VPN virtual server, ICA Proxy, CVPN, RDP Proxy, or 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 servers. Additionally, CR virtual servers of type HDX are also impacted. The vulnerability is due to improper bounds checking on memory buffers, allowing an attacker to overflow memory and execute arbitrary code or crash the system. The CVSS 4.0 vector indicates network attack vector (AV:N), high attack complexity (AC:H), no privileges required (PR:N), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (C:H, I:H, A:H). Although no known exploits are publicly reported yet, the critical severity and ease of remote exploitation without authentication make this a significant threat. The vulnerability affects core functions such as VPN access and load balancing, which are critical for enterprise network infrastructure and remote access services.

For European organizations, the impact of CVE-2025-7775 is substantial due to the widespread use of Citrix NetScaler ADC and Gateway appliances in enterprise environments for secure remote access, application delivery, and load balancing. Successful exploitation could allow attackers to execute arbitrary code remotely, potentially leading to full system compromise, data breaches, or disruption of critical services. This is particularly concerning for organizations relying on IPv6 configurations and VPN services, which are common in modern network architectures. The resulting denial of service could disrupt business continuity, affecting operations, customer access, and internal communications. Confidentiality breaches could expose sensitive corporate or personal data, violating GDPR and other regulatory requirements. The lack of required authentication or user interaction lowers the barrier for attackers, increasing the risk of automated or widespread attacks. Given the critical infrastructure role of NetScaler devices, exploitation could also impact sectors such as finance, healthcare, government, and telecommunications across Europe.

1. Monitor Citrix advisories closely and apply official patches or updates as soon as they are released to remediate the vulnerability. 2. Until patches are available, restrict network access to NetScaler ADC and Gateway management interfaces and virtual servers, especially those configured as VPN or load balancing servers with IPv6. 3. Implement strict firewall rules to limit exposure of vulnerable services to trusted IP addresses only. 4. Disable or avoid using IPv6 bindings on load balancing virtual servers if not essential, as these configurations are specifically vulnerable. 5. Employ network segmentation to isolate NetScaler devices from general user networks and reduce attack surface. 6. Enable and review detailed logging and intrusion detection/prevention systems to detect anomalous traffic patterns or exploitation attempts targeting NetScaler appliances. 7. Conduct internal vulnerability scans and penetration tests focusing on NetScaler configurations to identify exposure. 8. Educate IT staff on the vulnerability specifics to ensure rapid response and mitigation. 9. Consider temporary alternative remote access solutions if patching cannot be immediately performed and risk is high. 10. Maintain backups and incident response plans tailored to potential NetScaler compromise scenarios.