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, this vulnerability manifests when NetScaler is configured as a Gateway using VPN virtual server, ICA Proxy, CVPN, or RDP Proxy with a PCoIP Profile bound to it. The vulnerability allows an attacker to trigger a memory overflow condition, which can lead to unpredictable or erroneous behavior including Denial of Service (DoS). The vulnerability affects multiple versions of NetScaler ADC: 14.1, 13.1 (including FIPS and NDcPP variants), and 12.1 (FIPS and NDcPP). The CVSS v4.0 score is 8.8, indicating a high severity level. The vector metrics indicate that the vulnerability is remotely exploitable over the network without requiring authentication or user interaction, with low attack complexity. The impact on confidentiality and integrity is low, but availability impact is high, meaning the primary consequence is service disruption. No known exploits are currently reported in the wild, and no patches or mitigations have been published yet. This vulnerability arises from improper bounds checking in memory operations related to the PCoIP profile handling, which can cause buffer overflow conditions leading to crashes or unstable behavior of the NetScaler ADC/Gateway services.

For European organizations, the impact of this vulnerability is significant, especially for those relying on Citrix NetScaler ADC and Gateway appliances to provide secure remote access and application delivery. The vulnerability could be exploited by remote attackers to cause Denial of Service, disrupting VPN and proxy services critical for remote workforce connectivity, application access, and business continuity. This disruption could affect sectors heavily dependent on remote access technologies such as finance, healthcare, government, and critical infrastructure. Given the lack of authentication or user interaction requirements, exploitation could be automated and widespread if weaponized. The availability impact could lead to operational downtime, loss of productivity, and potential cascading effects on dependent services. Although confidentiality and integrity impacts are low, the service disruption alone can have severe business consequences. Additionally, the presence of FIPS and NDcPP certified versions among the affected products indicates that even organizations with high security compliance requirements are vulnerable, potentially complicating compliance and risk management efforts.

1. Immediate mitigation should focus on network-level protections: restrict access to NetScaler ADC/Gateway management and VPN interfaces to trusted IP ranges and implement strict firewall rules to limit exposure. 2. Monitor network traffic and system logs for abnormal behavior or crashes related to VPN or proxy services, which may indicate attempted exploitation. 3. Employ intrusion detection/prevention systems (IDS/IPS) with updated signatures once available to detect exploitation attempts. 4. Engage with Citrix support and subscribe to official advisories to obtain patches or hotfixes as soon as they are released. 5. If possible, temporarily disable or avoid using the PCoIP profile binding on VPN virtual servers or proxies until a patch is applied. 6. Conduct thorough testing of any applied patches in a controlled environment before deployment to production to avoid service disruptions. 7. Review and update incident response plans to include scenarios involving VPN service outages and potential exploitation of this vulnerability. 8. For organizations using FIPS or NDcPP certified versions, coordinate with compliance teams to document risk acceptance or mitigation steps taken.