Citrix NetScaler ADC and Gateway contain a buffer overflow vulnerability leading to unintended control flow and Denial of Service. NetScaler must be configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server.
Citrix · NetScaler ADC and Gateway
Known ransomware use: Unknown
Follow the source advisory and validate exposure in your environment.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Recent reporting that mentions CVE-2025-6543.
The Dutch National Cyber Security Centre (NCSC-NL) has warned of cyber attacks exploiting a recently disclosed critical security flaw impacting Citrix NetScaler ADC products to breach organizations in the country
The Netherlands' National Cyber Security Centre (NCSC) is warning that a critical Citrix NetScaler vulnerability tracked as CVE-2025-6543 was exploited to breach "critical organizations" in the country. [...]
Citrix is warning that a vulnerability in NetScaler appliances tracked as CVE-2025-6543 is being actively exploited in the wild, causing devices to enter a denial of service condition. [...]
Citrix has released security updates to address a critical flaw affecting NetScaler ADC that it said has been exploited in the wild