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. The flaw arises in scenarios where NetScaler is configured as a Gateway (including VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or as an AAA virtual server. Additionally, the vulnerability impacts load balancing (LB) virtual servers of types HTTP, SSL, or HTTP_QUIC when bound with IPv6 services or service groups, including DBS IPv6 services or DBS IPv6 servers. It also affects CR virtual servers of type HDX. The vulnerability allows an attacker to trigger a memory overflow condition, which can lead to remote code execution (RCE) or denial of service (DoS). The CVSS v4.0 score is 9.2, indicating critical severity. The 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 (VC:H, VI:H, VA:H). The scope is limited (S:L), and the exploit requires partial attack complexity and partial privileges, but no 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. No known exploits in the wild have been reported yet. The vulnerability stems from improper bounds checking on memory buffers when processing specific network traffic or configurations involving IPv6 services and virtual server types. Successful exploitation could allow an unauthenticated remote attacker to execute arbitrary code on the device or cause a denial of service, potentially disrupting critical network services and VPN access.

For European organizations, the impact of CVE-2025-7775 is significant due to the widespread use of Citrix NetScaler ADC and Gateway appliances in enterprise environments for secure remote access, load balancing, and application delivery. Exploitation could lead to full compromise of the affected appliance, allowing attackers to execute arbitrary code, potentially gaining control over network traffic, intercepting or modifying sensitive data, or disrupting availability of critical services such as VPNs and remote desktop access. This could result in data breaches, operational downtime, and loss of trust. Given the critical role of these devices in secure remote access and application delivery, disruption could impact business continuity, especially for sectors relying heavily on remote work and secure application access, such as finance, healthcare, and government. The vulnerability’s ability to be exploited remotely without authentication and without user interaction increases the risk of widespread attacks. Additionally, the involvement of IPv6 services broadens the attack surface as IPv6 adoption grows in European networks. The lack of known exploits in the wild currently provides a window for mitigation, but the critical severity demands immediate attention.

1. Immediate application of vendor-provided patches or updates once available is the most effective mitigation. Organizations should monitor Citrix advisories closely for patch releases addressing CVE-2025-7775. 2. In the interim, restrict network access to NetScaler ADC and Gateway management interfaces and virtual servers to trusted IP ranges using firewall rules and access control lists (ACLs). 3. Disable or avoid configurations involving IPv6 services or service groups on affected virtual servers if not strictly necessary, as these configurations are specifically implicated in the vulnerability. 4. Employ network segmentation to isolate NetScaler appliances from untrusted networks and limit exposure. 5. Monitor network traffic and logs for anomalous activity targeting NetScaler devices, including unusual requests to VPN or load balancing virtual servers. 6. Implement intrusion detection/prevention systems (IDS/IPS) with updated signatures to detect attempts to exploit this vulnerability once signatures become available. 7. Conduct regular vulnerability scans and penetration tests focusing on NetScaler appliances to identify potential exploitation attempts. 8. Prepare incident response plans specific to potential compromise of NetScaler devices, including backup and recovery procedures.