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NetScaler ADC and NetScaler Gateway Security Bulletin for CVE-2026-8451, CVE-2026-8452, CVE-2026-8655, CVE-2026-10816, CVE-2026-10817, and CVE-2026-13474

Gedeon Richemond

4 min read

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NetScaler ADC and NetScaler Gateway Security Bulletin for CVE-2026-8451, CVE-2026-8452, CVE-2026-8655, CVE-2026-10816, CVE-2026-10817, and CVE-2026-13474

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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

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.

 

Summary
CVE-ID Description Pre-conditionsCWECVSSv4

CVE-2026-8451		Insufficient input validation leading to memory overreadNetScaler ADC or NetScaler Gateway must be configured as a SAML IDPCWE-125: Out-of-bounds ReadCVSS v4.0 Base Score: 8.8 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:H/SC:N/SI:N/SA:N )

CVE-2026-8452
Memory overflow vulnerability leading to unpredictable or erroneous behavior and Denial of ServiceAppliance must be configured as:
Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy)
OR
AAA virtual server		CWE-119 – Improper Restriction of Operations within the Bounds of a Memory BufferCVSS v4.0 Base Score: 8.8
(CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:H/SC:L/SI:L/SA:L)

CVE-2026-8655Multiple Memory overflow vulnerabilities leading to unpredictable or erroneous behavior and Denial of ServiceNetScaler ADC must be configured as an LB of type Oracle
OR
 
NetScaler ADC must be configured as a DNS Proxy
OR 
NetScaler ADC must be configured as a DNS recursive resolver deployment		CWE-119 – Improper Restriction of Operations within the Bounds of a Memory BufferCVSS v4.0 Base Score: 8.8
(CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:L)

CVE-2026-10816

Arbitrary File Read (Unauthenticated)
Access to NSIP, Cluster Management IP or SNIP with management access enabledCWE-73: External Control of File Name or PathCVSS v4.0 Base Score: 7.1 ( CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N )

CVE-2026-10817
Insufficient input validation leading to memory overreadTCP TimeStamp enabled in TCP Profile and associated with the virtual server (of type LB, CS, VPN) or the service configured on NetScaler
CWE-125: Out-of-bounds Read
CVSS v4.0 Base Score: 6.9 ( CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N )

CVE-2026-13474
Denial of service via malformed HTTP/2 requestsHTTP/2 enabled in HTTP Profile and associated with the virtual server (of type LB, CS, VPN) or the service configured on NetScalerCWE-401:Missing Release of Memory after Effective LifetimeCVSS v4.0 Base Score: 8.7 ( CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L )
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 assignme
More Information

https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX696604&articleTitle=CTX696604_NetScaler_ADC_and_NetScaler_Gateway_Security_Bulletin_for_CVE_2026_8451_CVE_2026_8452_CVE_2026_8655_CVE_2026_10816_CVE_2026_10817_and_CVE_2026_13474