CVE-2025-6543
Published 2025-06-25 · Updated 2026-06-17 · Source secure@citrix.com
Summary
CVE-2025-6543 is a critical-severity (CVSS 9.8) vulnerability in Citrix NetScaler ADC and Gateway. CISA added it to the Known Exploited Vulnerabilities catalog on June 30, 2025, which means exploitation in the wild has been confirmed; US federal agencies had to remediate it by July 21, 2025. CISA does not currently list it as used in ransomware campaigns. Citrix has 27 vulnerabilities in the KEV catalog, 7 of them linked to ransomware.
All 27 known-exploited Citrix vulnerabilities →Description
Memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and NetScaler Gateway when configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CISA Known-Exploited Vulnerability
Product: Citrix — NetScaler ADC and Gateway
Name: Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability
Date added: 2025-06-30 · Due: 2025-07-21
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.