NetScaler ADC and NetScaler Gateway are affected by the vulnerabilities mentioned below:

What Customers Should Do

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 14.1-72.61 and later releases
• NetScaler ADC and NetScaler Gateway 13.1-63.18 and later releases of 13.1
• NetScaler ADC 14.1-FIPS 14.1-72.61 FIPS and later releases of 14.1-FIPS
• NetScaler ADC 13.1-FIPS and 13.1-NDcPP 13.1.37.272 and later releases of 13.1-FIPS and 13.1-NDcPP

CVE-2026-13474

Customers must upgrade to the above-mentioned NetScaler firmware versions that include the fix and update their configuration as described below. 
Configure the Http2SmallWndTimeout parameter, which controls the timeout (in seconds) for HTTP/2 small‑window stalled streams.

• For appliances using HTTP Strict Profiles, this parameter defaults to 30 seconds, and the fix is effective immediately after the upgrade.
• For appliances NOT using HTTP Strict Profiles, the default value is 0, and in that case, merely upgrading to the builds containing the fix WILL NOT address the vulnerability completely. In this case, customers must manually set Http2SmallWndTimeout to 30 seconds.

Please note that Http2SmallWndTimeout is a new parameter and is only available in the firmware builds that contain the fix.

Configuration command: 

set ns httpProfile <profile_name> -http2SmallWndTimeout <value_in_seconds> 

Steps to determine if an appliance meets the CVE preconditions

CVE-2026-8451: 

Customers can determine if the appliance meets the precondition by inspecting their NetScaler configuration for the specified string:

• add authentication samlIdPProfile .*

CVE-2026-8452 :  

Customers can determine if the appliance meets the precondition by inspecting their NetScaler configuration for the specified string:

• An Auth Server (AAA Vserver):
  • add authentication vserver .*
• A Gateway (VPN Vserver,  ICA Proxy, CVPN, RDP Proxy) :
  
  • add vpn vserver .*

CVE-2026-8655 :

Customers can determine if the appliance meets the precondition by inspecting their NetScaler configuration for the specified string:

• An LB or CS vserver of type Oracle(LB Vserver):
  
  • add lb vserver.*ORACLE.*
• A CS or LB vserver of type DNS,DNS_TCP,  DOT or SSL with DNSoverHTTPS enabled :
  
  • add cs vserver.*DNS.*
  • add lb vserver.*DNS.*
  • add cs vserver.*DOT.*
  • add lb vserver.*DOT.*
  • add cs vserver.*SSL.*dnsOverHttps.*
  • add lb vserver.*SSL.*dnsOverHttps.*    
• DNS global parameter or dns profile with recursive resolution enabled:
  
  • set dns parameter.*-recursion ENABLED.*
  • add dns profile.*recursiveResolution ENABLED

CVE-2026-10817:  

Customers can determine if the appliance meets the precondition by inspecting their NetScaler configuration for the specified string:

• Search for “TimeStamp ENABLED” to identify all TCP profiles that have the TimeStamp option enabled.     
• Then search for the identified TCP profile name to determine which vservers and services it is attached to.        

       Note: If TimeStamp is enabled on nstcp_default_profile, then all vservers and services that do not have an explicit TCP profile attached will be impacted, as they inherit nstcp_default_profile by default.
   
        Example:
        add ns tcpProfile custom_profile -TimeStamp ENABLED
        add lb vserver test_server HTTP 10.10.10.20 80 -persistenceType NONE -cltTimeout 180 -tcpProfileName custom_profile
        add service s1 20.20.20.2 HTTP 80 -gslb NONE -maxClient 0 -maxReq 0 -cip DISABLED -usip NO -useproxyport YES -sp OFF -cltTimeout 180 -svrTimeout 360 -CKA NO -TCPB NO -CMP NO -tcpProfileName custom_profile

CVE-2026-13474:  

Customers can determine if the appliance meets the precondition by inspecting their NetScaler configuration for the specified string:

• Profile Check: Identify if -http2 ENABLED is set on any HTTP profile. If none are found, the appliance is considered non-vulnerable.
• vServer Association: If such a profile exists, identify all LB, CS, and VPN vServers that reference it.
• Default Profile Handling: If default profile nshttp_default_profile has -http2 enabled, identify all vServers that utilize this default profile. (i.e., those without an explicit -httpProfileName assignment).
           

Acknowledgement

Cloud Software Group thanks Michael Tucker from the XOR team at JPMorgan Chase, Aliz Hammond of watchTowr, and Maxim Suhanov for working with us to protect our customers.

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Severity - High

Description of Problem

Multiple vulnerabilities have 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 14.1-72.61
• NetScaler ADC and NetScaler Gateway 13.1 BEFORE 13.1-63.18
• NetScaler ADC FIPS BEFORE 14.1-72.61 FIPS
• NetScaler ADC FIPS and NDcPP BEFORE 13.1-37.272

Note: 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.

What Citrix is Doing

Citrix is notifying customers and channel partners about this potential security issue through the publication of this security bulletin on the Citrix Knowledge Center at https://support.citrix.com/support-home/topic-article-list?trendingCategory=20&trendingTopicName=Security%20Bulletin  

Obtaining Support on This Issue

If you require technical assistance with this issue, please contact Citrix Technical Support. Contact details for Citrix Technical Support are available at https://support.citrix.com/support-home/home 

Subscribe to Receive Alerts

Citrix strongly recommends that all customers subscribe to receive alerts when a Citrix security bulletin is created or modified at https://support.citrix.com/wolken-support/view/aboutsupport/my-support-alerts  

Reporting Security Vulnerabilities to Citrix

Citrix welcomes input regarding the security of its products and considers any and all potential vulnerabilities seriously. For details on our vulnerability response process and guidance on how to report security-related issues to Citrix, please see the following webpage: https://www.cloud.com/trust-center/support 

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