Citrix has released a critical security bulletin addressing a vulnerability affecting NetScaler ADC (formerly Citrix ADC) and NetScaler Gateway (formerly Citrix Gateway). Citrix NetScaler is an all-in-one load balancer, web application firewall (WAF), virtual private network (VPN) gateway and SSL offloading tool for web applications.
- CVE-2025-6543 is a ‘memory overflow’ vulnerability with a CVSSv4 base score of 9.2. Successful exploitation could allow a remote unauthenticated attacker to gain unintended control flow and perform denial-of-service (DoS) in NetScaler ADC and NetScaler Gateway. NetScaler is only vulnerable to CVE-2025-6543 when configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server.
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Source: NHS Digital
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