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!
Attention! Please note the following regarding to this update:
Customers who already have transitioned to Netscaler LAS can upgrade without any special remarks. If you have not yet changed the Licensing mode, please check the requirements for LAS prior to the update!
Upgrading without proper LAS activation can lead to licensing issues. While these can be resolved by downloading a new file-based license, this workaround is only available until April 15, 2026.
Severity – Critical
Description of Problem
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:
CVE-2026-3055:
NetScaler ADC and NetScaler Gateway 14.1 BEFORE 14.1-66.59
NetScaler ADC and NetScaler Gateway 13.1 BEFORE 13.1-62.23
NetScaler ADC FIPS and NDcPP BEFORE 13.1-37.262
CVE-2026-4368:
NetScaler ADC and NetScaler Gateway 14.1-66.54
Note: This bulletin only applies to customer-managed NetScaler ADC and NetScaler Gateway. Cloud Software Group upgrades Citrix-managed cloud services and Citrix-managed Adaptive Authentication with the necessary software updates.
Details
NetScaler ADC and NetScaler Gateway are affected by the vulnerabilities mentioned below:
CVE-ID
Description
Pre-conditions
CWE
CVSS v4.0
CVE-2026-3055
Insufficient input validation leading to memory overread
Citrix ADC or Citrix Gateway must be configured as a SAML IDP
CWE-125: Out-of-bounds Read
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)
CVE-2026-4368
Race Condition leading to User Session Mixup
Appliance must be configured as:Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server
CWE-362: Race Condition
CVSS v4.0 Base Score: 7.7(CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N)
What Customers Should Do
CVE 2026-3055 was identified internally through our ongoing security reviews and broader efforts to strengthen the security of the product.
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 14.1-66.59 and later releases
NetScaler ADC and NetScaler Gateway 13.1-62.23 and later releases of 13.1
NetScaler ADC 13.1-FIPS and 13.1-NDcPP 13.1.37.262 and later releases of 13.1-FIPS and 13.1-NDcPP
Note: Customers are recommended to upgrade their appliances to one of the supported versions that address the vulnerabilities.
CVE-2026-3055 :
Customers can determine if they have an appliance configured as a SAML IDP Profile by inspecting their NetScaler Configuration for the specified string:
add authentication samlIdPProfile .*
CVE-2026-4368
Customers can determine if they have an appliance configured as one of the following by inspecting their NetScaler Configuration for the specified strings
An Auth Server (AAA Vserver):
add authentication vserver .*
A Gateway (VPN Vserver, ICA Proxy, CVPN, RDP Proxy) :
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 14.1-56.73
NetScaler ADC and NetScaler Gateway 13.1 BEFORE 13.1-60.32
NetScaler ADC 13.1-FIPS and NDcPP BEFORE 13.1-37.250-FIPS and NDcPP
NetScaler ADC 12.1-FIPS and NDcPP BEFORE 12.1-55.333-FIPS and NDcPP
Note: NetScaler ADC and NetScaler Gateway versions 12.1 and 13.0 are now End Of Life (EOL) and are vulnerable. Customers are recommended to upgrade their appliances to one of the supported versions that address the vulnerabilities.
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 are affected by the vulnerability mentioned below:
CVE-ID
Description
Pre-conditions
CWE
CVSSv4
CVE-2025-12101
Cross-Site Scripting (XSS)
NetScaler must be configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy)ORAAA virtual server
CWE-79: Improper Neutralization of Input During Web Page Generation (‚Cross-site Scripting‘)
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 14.1-56.73 and later releases
NetScaler ADC and NetScaler Gateway 13.1-60.32 and later releases of 13.1
NetScaler ADC 13.1-FIPS and 13.1-NDcPP 13.1-37.250 and later releases of 13.1-FIPS and 13.1-NDcPP
NetScaler ADC 12.1-FIPS and 12.1-NDcPP 12.1-55.333 and later releases of 12.1-FIPS and 12.1-NDcPP
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.
CVE-2025-12101 :
Customers can determine if they have an appliance configured as one of the following by inspecting their NetScaler Configuration for the specified strings
An Auth Server (AAA Vserver): add authentication vserver .*
Vor eingen Tagen hat Citrix eine MaIl an alle Kunden verschickt, mit der Information, dass ab dem 15. April 2026 das alte Lizenzmodell mit lokalen Lizenzfiles nicht mehr unterstützt wird. Statt dessen soll ab dann zwingend der neue License Activation Service (LAS) genutzt werden.
Kunden werden aufgefordert, baldmöglichst auf das neue LAS Lizenzverfahren umzustellen. Diese Umstellung erfordert ein Update aller Citrix Komponenten auf mindestens CR 2411, oder neuer.
Unglücklicherweise treten bei diversen Produkten nach der Installation Lizenzierungsprobleme auf. Welche Probleme auftreten, hängt von diversen Parametern ab. So spielt das Alter der lokalen Lizenzfiles, aber auch das Lizenzmodell (Universal, HMC, Citrix for Private Cloud, etc.) eine Rolle. Zusammen mit den unterschiedliche Citrix Produkten (CVAD, PVS, Lizenz Server, XenServer, etc.) ergibt sich eine recht grosse Matrix mit unterschiedlichsten Problemen.
Bei diversen Kunden wurden teils gravierende Probleme entdeckt. So funktioniert nach dem Update auf 2507 LTSR, abhängig vom Lizenzmodell, entweder PVS nicht mehr, siehe https://support.citrix.com/external/article/695191/citrix-provisioning-services-reports-the.html, oder alle Mitarbeiter erhalten in ihrer Citrix Session ein Pop-Up mit der Info, dass die Umgebung ungenügend lizenziert ist und in 30 Tagen aufhört zu funktionieren.
AXACOM empfiehlt daher allen Kunden, momentan keine Updates ihrer CVAD-, Lizenz- und PVS-Server durchzuführen und zu warten, bis die Probleme behoben sind.
After upgrading NetScaler to build 14.1 47.46 or 13.1 59.19 customers might experience issues with Authentication.This can manifest as a «broken» login page, especially when using authentication methods like DUO configurations based on Radius authentication, SAML, or any Identity Provider (IDP) that relies on custom scripts.
Note : This behavior can possibly be due to the Content Security Policy (CSP) header being enabled by default in this NetScaler build, especially when CSP was not enabled prior to the upgrade.
Lösung
To resolve this issue temporarily, you need to disable the default CSP header on your NetScaler appliance. After disabling, it’s recommended to flush the cache to ensure the changes take effect immediately.
To ensure that your configurations work with CSP , please reach out to the support team so that we can identify the issue and fix it for your configuration.
Steps to Disable CSP Header:
Using Command Line Interface (CLI): Execute the following commands from Netscaler CLI:
set aaa parameter -defaultCSPHeader DISABLED
save ns config
Using Graphical User Interface (GUI):
Step 1: Log in to the NetScaler GUI.
Step 2: Navigate to NetScaler Gateway > Global Settings.
Step 3: Under the «Authentication Settings» section, click on Change authentication AAA settings.
Step 4: On the «Configure AAA Parameters» page, locate the Default CSP Header field. From the dropdown menu, select DISABLED.
Click OK to save the changes.
Post-Configuration Recommendation:
While enabling or disabling the default CSP policy, you are recommended to run the following command in the CLI
flush cache contentgroup loginstaticobjects
After performing the steps above, attempt to access your NetScaler Gateway authentication portal to validate if the issue is resolved.
Zusatz
Bei Fragen und Problemen können Sie sich gerne an Ihren AXACOM Verantwortlichen wenden.
