Citrix · NetScaler ADC and Gateway
CVE-2025-6543
Memory overflow vulnerability leading to unintended control flow and Denial of Service
What it is
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
CISA: 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.
What to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Deadline for US federal agencies: July 21, 2025
More exploited flaws from Citrix
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Jul 10, 2025 | Out-of-Bounds Read | NetScaler ADC and Gateway | Critical 9.3 | >99.9% |
| Oct 4, 2026 | Improper Restriction of Operations within the Bounds of a Memory Buffer | NetScaler | High 8.7 | 11% |
| Sep 27, 2026 | Improper Input Validation | NetScaler | Critical 9.5 | 82% |
| Sep 27, 2026 | Improper Restriction of Operations within the Bounds of a Memory Buffer | NetScaler | Critical 9.5 | 78% |
| Sep 9, 2026 | Authentication Bypass Using an Alternate Path or Channel | NetScaler | Critical 9.3 | 33% |
| Aug 26, 2026 | Improper Restriction of Operations within the Bounds of a Memory Buffer | NetScaler ADC and NetScaler Gateway | High 8.8 | 1.0% |
| Mar 30, 2026 | Out-of-Bounds Read | NetScaler | Critical 9.3 | 91% |
| Aug 26, 2025 | Memory Overflow | NetScaler | Critical 9.2 | 21% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.