Citrix hat für NetScaler 2 neue CVEs (Base Score: 9.3) veröffentlicht. Die Severity wurde als «Kritisch» eingestuft. Es sind alle NetScaler mit AAA und Gateway in Version 13.1 und 14.1 betroffen.
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 14.1-73.32
NetScaler ADC and NetScaler Gateway 13.1 BEFORE 13.1-63.21
NetScaler ADC FIPS BEFORE 14.1-73.32 FIPS
NetScaler ADC FIPS and NDcPP BEFORE 13.1-37.277
Additional 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.
Summary:
NetScaler ADC and NetScaler Gateway are affected by the vulnerabilities mentioned below
CVE-ID
Description
Pre-conditions
CWE
CVSSv4
CVE-2026-19489
Memory overflow vulnerability leading to unpredictable behavior or Denial of Service
SIP ALG(Session Initiation Protocol Application Layer Gateway) should be enabled on a Large Scale NAT (LSN) group configuration.
CWE-119 – Improper Restriction of Operations within the Bounds of a Memory Buffer
CVSS 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-2026-19490
Authentication bypass using an alternate path
The appliance must be configured as a Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy) or an AAA virtual server, subject to the following version-specific requirements:14.1-43.56 or later: Applicable only when configured with a SAML action.
14.1-43.55 or earlier: Applicable when configured with Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy ) or AAA vserver
13.1-61.28 or later: Applicable only when configured with a SAML action.
13.1-61.27 or earlier: Applicable when configured with Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy) or AAA vserver
13.1 FIPS: Applicable when configured with Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy) or AAA vserver.
CWE-288: Authentication Bypass Using an Alternate Path
CVSS v4.0 Base Score: 9.3(CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/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 14.1-73.32 and later releases
NetScaler ADC and NetScaler Gateway 13.1-63.21 and later releases of 13.1
NetScaler ADC 14.1-FIPS 14.1-73.32 FIPS and later releases of 14.1-FIPS
NetScaler ADC 13.1-FIPS and 13.1-NDcPP 13.1-37.277 and later releases of 13.1-FIPS and 13.1-NDcPP
Steps to determine if an appliance meets the CVE preconditions
For CVE-2026-19489:
Customers can determine if the appliance meets the precondition by inspecting their NetScaler configuration for the specified string:
«add lsn group.*sipalg.*»
For CVE-2026-19490:
Customers can determine if the appliance meets the precondition by inspecting their NetScaler configuration for the specified string:
An issue has been identified in the XenServer management API SDK that may allow an attacker on the management network who is able to intercept specific HTTPS requests within a higher-level operation to be able to act with the privileges of the intercepted administrator. This issue affects the XenCenter management agent together with third-party PowerShell and C# SDK clients.
This issue has the following identifier:
CVE-2026-42491
Affected Versions
This issue affects XenCenter versions before 2026.4.0 and, for PowerShell and C# clients only, SDK versions before 26.15.0. As the issue is in the client-side (XenCenter and SDK) code, it is independent of the version of XenServer that is in use.
Vulnerabilities have been discovered in the Citrix Secure Access Client for Windows and Citrix Endpoint Analysis Client. Refer to the information below for further details:
Affected Versions:
The following supported versions of Citrix Secure Access Client for Windows and Citrix Endpoint Analysis Client for Windows are affected by CVE-2026-53565:
Citrix Secure Access Client for Windows versions BEFORE 26.6.1.20
Citrix Endpoint Analysis Client for Windows versions BEFORE 26.5.1.7
The following supported versions of Citrix Secure Access Client for Windows are affected by CVE-2026-53566:
Citrix Secure Access Client for Windows versions BEFORE 26.6.1.20
Details
Citrix Secure Access Client for Windows and Citrix Endpoint Analysis Client for Windows contain the vulnerabilities mentioned below
CVE-ID
Description
Affected Products
Pre-conditions
CWE
CVSSv4
CVE-2026-53565
Local Privilege escalation allows a low-privileged user to gain SYSTEM privileges
Citrix Secure Access Client for Windows AND Citrix Endpoint Analysis Client for Windows
Standard user access on local system
CWE-269: Improper Privilege Management
CVSS v4.0 Base Score: 8.5(CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N)
CVE-2026-53566
Out-of-bounds memory read
Citrix Secure Access Client for Windows
Standard user access on local system and DNE driver is not installed
CWE-125: Out-of-bounds Read
CVSS v4.0 Base Score: 6.8 CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
What Customers Should Do
Cloud Software Group strongly urges customers of Citrix Secure Access Client for Windows and Citrix Endpoint Analysis Client to install the relevant updated versions as soon as possible:
Citrix Secure Access Client for Windows 26.6.1.20 and later releases
Citrix Endpoint Analysis Client for Windows 26.5.1.7 and later releases
Steps to determine if an appliance meets the CVE preconditions
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.
Disclaimer
The information on this page is being provided to you on an «AS IS» and «AS-AVAILABLE» basis. The issues described on this page may or may not impact your system(s). Cloud Software Group, Inc. and its subsidiaries (collectively, «Cloud SG») make no representations, warranties, or guarantees as to the information contained herein. ANY AND ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY, NON-INFRINGEMENT AND FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED. BY ACCESSING THIS PAGE, YOU ACKNOWLEDGE THAT CLOUD SG SHALL IN NO EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES THAT ARISE OUT OF YOUR USE OR FAILURE TO USE THE INFORMATION CONTAINED HEREIN. Cloud SG reserves the right to change or update the information on this page at any time. We accordingly recommend that you always view the latest version of this page. The information contained herein is being provided to you under the terms of your applicable customer agreement with Cloud SG, and may be used only for the purposes contemplated by such agreement. If you do not have such an agreement with Cloud SG, this information is provided under the cloud.com Terms of Use, and may be used only for the purposes contemplated by such Terms of Use.
Details
NetScaler ADC and NetScaler Gateway are affected by the vulnerabilities mentioned below:
CVE-ID
Description
Pre-conditions
CWE
CVSSv4
CVE-2026-8451
Insufficient input validation leading to memory overread
NetScaler ADC or NetScaler Gateway must be configured as a SAML IDP
CWE-125: Out-of-bounds Read
CVSS 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 Service
Appliance must be configured as: Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy)ORAAA virtual server
CWE-119 – Improper Restriction of Operations within the Bounds of a Memory Buffer
CVSS 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-2026-8655
Multiple Memory overflow vulnerabilities leading to unpredictable or erroneous behavior and Denial of Service
NetScaler ADC must be configured as an LB of type OracleOR NetScaler ADC must be configured as a DNS ProxyOR NetScaler ADC must be configured as a DNS recursive resolver deployment
CWE-119 – Improper Restriction of Operations within the Bounds of a Memory Buffer
CVSS 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 enabled
CWE-73: External Control of File Name or Path
CVSS 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 overread
TCP 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 requests
HTTP/2 enabled in HTTP Profile and associated with the virtual server (of type LB, CS, VPN) or the service configured on NetScaler
CWE-401:Missing Release of Memory after Effective Lifetime
CVSS 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 assignment).
Zukunftssichere Zertifikatsverwaltung im Zeitalter der 47-Tage-Zyklen – effizient, ressourcenschonend und vollautomatisch.
Die Lebensdauer von SSL/TLS-Zertifikaten sinkt bis 2029 drastisch. Die vom CA/B Forum beschlossene Massnahme sieht vor, die Gültigkeitsdauer von Zertifikaten schrittweise von derzeit 199 Tagen auf 47 Tage zu verkürzen. Somit wird aus einer jährlichen Aufgabe bald eine monatliche Pflicht. Für Unternehmen, die Citrix Netscaler (ADC) im Einsatz haben, bedeutet diese Entwicklung das Ende der manuellen Zertifikatsverwaltung. Unsere leichtgewichtige, ACME-basierte Automatisierungslösung für Netscaler schliesst genau diese Lücke. Mit einem minimalen Footprint, breiter CA-Unterstützung und flexiblen Betriebsmodellen.
Mit unserer ACME-basierten Automatisierung profitieren Sie von:
100% Vermeidung von Service-Ausfällen durch abgelaufene Zertifikate.
Breiter nativer Unterstützung für ACME fähige CAs wie z.B. Let’s Encrypt, Buypass, Digicert, Google, SSL.com und insbesondere ZeroSSL.
Was macht unsere ROX Zertifikat-Automatisierung besonders?
Im Gegensatz zu schwerfälligen PKI-Lösungen ist unsere Architektur auf das Wesentliche reduziert und kommt ohne aufwendige Server- oder Datenbankstrukturen aus. Alles, was vorausgesetzt wird, ist eine kleine, gehärtete Linux-basierte virtuelle Maschine (VM). Diese agiert als intelligenter Broker zwischen Ihren Netscalern und der Certificate Authority (CA) und wickelt den gesamten Lebenszyklus der Zertifikate vollautomatisch über den ACME-Standard ab. Nach der initialen Einrichtung erneuern und binden sich die Zertifikate auf den Netscalern völlig selbstständig – inklusive automatischer Speicherung der Config.
Unsere Empfehlung: ZeroSSL Obwohl unsere Lösung flexibel verschiedenste CAs unterstützt, empfehlen wir bevorzugt den Einsatz von ZeroSSL. Als europäischer Dienst bietet ZeroSSL nicht nur einen klaren Heimvorteil in puncto Datenschutz und Zuverlässigkeit, sondern besticht technisch vor allem durch seine sehr einfache und robuste Integration. Dies garantiert einen besonders reibungslosen, fehlerfreien Automatisierungsprozess in Ihrer Infrastruktur.
Unsere ROX Appliance gibt es in zwei Varianten: Entweder als komplett durch uns betriebenen Managed Service für Ihre maximale Entlastung oder als On-Premises/Cloud-Variante für volle Kontrolle durch Ihr eigenes Team.
Skalieren Sie dynamisch, reduzieren Sie Kosten und schützen Sie Ihre geschäftskritischen Anwendungen mit höchster Sicherheit. Die ROX NetScaler SSL-Automatisierung ebnet Ihnen den Weg ins neue Web-Zeitalter.
Haben Sie Fragen oder möchten mehr erfahren? Wir sind immer für Sie da – kontaktieren Sie uns einfach!
Unser Lösung wird stetig weiter entwickelt, in Zukunft streben wir an auch andere Umsysteme anzubinden, z.B. Microsoft IIS, MS Exchange, usw. Sprechen Sie uns darauf an!
Kunden, die auf ihrem NetScaler Kerberos für SSO PreAuthentication verwenden, bekommen nach dem Microsoft April Update ein Problem. Kerberos Negogiate (SSO) funktioniert danach nicht mehr mit dem NetScaler und auch weitere Umsysteme können davon betroffen sein. Sie erhalten bei einem Login Versuch via NetScaler folgenden Eintrag im ns.log:
default AAATM Message 97485 0 : "NS kerberos: Failed to verifiy negotiate data with errcode 983044"
Umgemünzt auf den NetScaler bedeutet dies dass der Wert 1, temporär wieder RC4 Kerberos Ticket für Netscaler SPNs erlaubt. Nach dem RegKey verändern ist ein gestaffelter DC reboot erforderlich!
ACHTUNG: Diese Anpassungen sind nur als Workaround zu verstehen und sollten wieder rückgängig gemacht werden, sobald Citrix einen Fix für den Fehler bereitstellt!
Update 08.05.2026 – Problemlösung
Allgemeine Voraussetzung
Der zugehörige AD Service Account muss AES 125 bit und oder AES 256 bit erlauben
Danach das KeyTab File neu erzeugen und KeyTab File am Netscaler ersetzen. Ganz wichtig dabei ist die Grossschreibung!
