CVE-2025-7776 is a high-severity 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. Specifically, the flaw manifests when NetScaler is configured as a Gateway—such as VPN virtual server, ICA Proxy, CVPN, or RDP Proxy—with a PCoIP Profile bound to it. The vulnerability arises from improper handling of memory buffers, which can lead to memory overflow conditions. This can cause unpredictable or erroneous behavior including denial of service (DoS) conditions. The affected versions include NetScaler ADC versions 14.1, 13.1 (including FIPS and NDcPP variants), and 12.1 (FIPS and NDcPP). The vulnerability is remotely exploitable without authentication or user interaction, as indicated by the CVSS 4.0 vector (AV:N/AC:L/PR:N/UI:N). The impact on confidentiality and integrity is low, but availability impact is high due to potential DoS. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was reserved in mid-July 2025 and published in late August 2025, indicating recent discovery and disclosure. Given the critical role of NetScaler ADC and Gateway appliances in enterprise network infrastructure—especially for secure remote access and application delivery—this vulnerability poses a significant risk to organizations relying on these products for VPN and proxy services.

For European organizations, the impact of CVE-2025-7776 can be substantial. NetScaler ADC and Gateway appliances are widely used in enterprise environments to provide secure remote access, load balancing, and application delivery. A successful exploitation could lead to denial of service, disrupting remote access capabilities and potentially halting critical business operations, especially for organizations with a distributed workforce or those relying heavily on VPNs and remote desktop services. This disruption could affect sectors such as finance, healthcare, government, and critical infrastructure, where availability and continuity are paramount. Additionally, the lack of required authentication for exploitation increases the risk of external attackers causing outages. While confidentiality and integrity impacts are rated low, the availability impact alone can cause significant operational and reputational damage. The absence of known exploits in the wild currently provides a window for mitigation, but the high CVSS score and ease of exploitation warrant immediate attention.

Given the absence of published patches at this time, European organizations should implement the following specific mitigations: 1) Immediately audit all NetScaler ADC and Gateway deployments to identify configurations using PCoIP Profiles bound to Gateway virtual servers (VPN, ICA Proxy, CVPN, RDP Proxy). 2) Where feasible, temporarily disable or remove PCoIP Profiles from Gateway configurations until patches are available. 3) Employ network-level protections such as strict firewall rules and access control lists to limit exposure of NetScaler Gateway interfaces to trusted IP ranges only. 4) Monitor NetScaler logs and network traffic for unusual activity or signs of attempted exploitation, focusing on gateway-related traffic. 5) Engage with Citrix support and subscribe to their security advisories to obtain patches or workarounds as soon as they are released. 6) Consider deploying intrusion prevention systems (IPS) with updated signatures once available to detect exploitation attempts. 7) For critical environments, implement redundancy and failover mechanisms to minimize downtime in case of DoS incidents. These targeted actions go beyond generic advice by focusing on the specific vulnerable configuration and limiting attack surface exposure until official patches are deployed.