Description of Problem
A vulnerability has been discovered in NetScaler ADC (formerly Citrix ADC) and NetScaler Gateway (formerly Citrix Gateway). Refer below for further details.

Affected Versions
The following supported versions of NetScaler ADC and NetScaler Gateway are affected by the vulnerabilities:

NetScaler ADC and NetScaler Gateway 14.1 BEFORE 14.1-47.46
NetScaler ADC and NetScaler Gateway 13.1 BEFORE 13.1-59.19
NetScaler ADC 13.1-FIPS and NDcPP BEFORE 13.1-37.236-FIPS and NDcPP

NetScaler ADC 12.1-FIPS is not affected by this vulnerability.

Additional Note: Secure Private Access on-prem or Secure Private Access Hybrid deployments using NetScaler instances are also affected by the vulnerabilities. Customers need to upgrade these NetScaler instances to the recommended NetScaler builds to address the vulnerabilities.

This bulletin only applies to customer-managed NetScaler ADC and NetScaler Gateway. Cloud Software Group upgrades the Citrix-managed cloud services and Citrix-managed Adaptive Authentication with the necessary software updates.

Details
NetScaler ADC and NetScaler Gateway contain the vulnerability mentioned below:

CVE-ID

Description Pre-conditions CWE CVSSv4
CVE-2025-6543

Memory 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

CWE-119 - Improper Restriction of Operations within the Bounds of a Memory Buffer

CVSS v4.0 Base Score: 9.2

(CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L)

What Customers Should Do
Exploits of CVE-2025-6543 on unmitigated appliances have been observed.

Cloud Software Group strongly urges affected customers of NetScaler ADC and NetScaler Gateway to install the relevant updated versions as soon as possible.

NetScaler ADC and NetScaler Gateway 14.1-47.46 and later releases
NetScaler ADC and NetScaler Gateway 13.1-59.19 and later releases of 13.1
NetScaler ADC 13.1-FIPS and 13.1-NDcPP 13.1-37.236 and later releases of 13.1-FIPS and 13.1-NDcPP. Customers should contact support - https://support.citrix.com/support-home/home to obtain the 13.1-FIPS and 13.1-NDcPP builds that address this issue.

Note: NetScaler ADC and NetScaler Gateway versions 12.1 and 13.0 are now End Of Life (EOL) and no longer supported. Customers are recommended to upgrade their appliances to one of the supported versions that address the vulnerabilities.