Multiple vulnerabilities have been discovered in Citrix NetScaler ADC (formerly Citrix ADC) and Citrix NetScaler Gateway (formerly Citrix Gateway). Refer below for further details.
Affected Versions:
The following supported versions of Citrix NetScaler ADC and Citrix NetScaler Gateway are affected by the vulnerabilities:
Citrix NetScaler ADC and Citrix NetScaler Gateway 14.1 BEFORE 14.1-73.37
Citrix NetScaler ADC and Citrix NetScaler Gateway 13.1 BEFORE 13.1-64.23
Citrix NetScaler ADC FIPS BEFORE 14.1-73.37 FIPS
Citrix NetScaler ADC FIPS and NDcPP BEFORE 13.1-37.279
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 Citrix NetScaler ADC (“NetScaler ADC”) and Citrix NetScaler Gateway (“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 Holdings, Inc. and its affiliates, including Citrix Systems, Inc. (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. Cloud SG accordingly recommends 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
Citrix NetScaler ADC and Citrix NetScaler Gateway are affected by the vulnerabilities identified below
CVE-ID
Description
Pre-conditions
CWE
CVSSv4
CVE-2026-88771
A remote code execution vulnerability exists due to improper input validation, which can allow an unauthenticated attacker to execute arbitrary commands
All NetScaler ADC and NetScaler Gateway deployments (Default configuration / No additional feature required)
CWE-20: Improper Input Validation
CVSS v4.0 Base Score: 9.5 (CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H)
CVE-2026-88772
Memory overflow vulnerability leading to Remote Code Execution or Denial of Service
DTLS configuration enabled on NetScaler ADC or NetScaler Gateway (Note: Enabled by default on VPN vServer)
CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer
CVSS v4.0 Base Score: 9.5 (CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H)
CVE-2026-88773
HTTP Request Smuggling
HTTP Configuration enabled on NetScaler ADC or NetScaler Gateway
CWE-444: Inconsistent Interpretation of HTTP Requests (‚HTTP Request/Response Smuggling‘)
CVSS v4.0 Base Score: 9.3 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N)
CVE-2026-88774
Feature policy bypass due to improper HTTP URL based expression usage
Any policy expression configured with HTTP URL based expression
CWE-16: Configuration
CVSS v4.0 Base Score:7 (CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N)
CVE-2026-88775
Memory overflow vulnerability leading to unpredictable or erroneous behavior or Denial of Service
NetScaler ADC or NetScaler Gateway configured as either:• Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy)• AAA 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:L/VI:L/VA:H/SC:N/SI:N/SA:N)
CVE-2026-88776
Memory overflow vulnerability leading to unpredictable or erroneous behavior or Denial of Service
Configured as a Load Balancing (LB) virtual server of type Oracle on NetScaler ADC or NetScaler Gateway
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:N)
CVE-2026-88777
Memory overflow vulnerability leading to unpredictable or erroneous behavior or Denial of Service
Configured as an LB/CS or CGNAT-LSN/NAT64 device with a non-HTTP L7 protocol feature enabled on NetScaler ADC or NetScaler Gateway
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:N)
CVE-2026-88778
TCP Initial Sequence Number (ISN) prediction
TCP Configuration enabled on NetScaler ADC or NetScaler Gateway
CWE-342: Predictable Exact Value from Previous Values
CVSS v4.0 Base Score: 8.8 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:H/SC:L/SI:L/SA:L)
What Customers Should Do
Exploits of CVE-2026-88771 and CVE-2026-88772 on unmitigated NetScaler deployments 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.
Citrix NetScaler ADC and Citrix NetScaler Gateway 14.1-73.37 and later releases
Citrix NetScaler ADC and Citrix NetScaler Gateway 13.1-64.23 and later releases of 13.1
Citrix NetScaler ADC 14.1-FIPS 14.1-73.37 FIPS and later releases of 14.1-FIPS
Citrix NetScaler ADC 13.1-FIPS and 13.1-NDcPP 13.1.37.279 and later releases of 13.1-FIPS and 13.1-NDcPP
Steps to determine if an appliance meets the CVE preconditions
CVE-2026-88771 Precondition: All NetScaler ADC and NetScaler Gateway deployments (Default configuration / No additional feature required)
Instructions: All NetScaler ADC and NetScaler Gateway deployments are affected, including those deployed with the default configuration. No additional features or settings need to be enabled for the NetScaler deployment to be vulnerable.
CVE-2026-88772 Precondition: DTLS configuration enabled on NetScaler ADC or NetScaler Gateway (Note: Enabled by default on VPN vServer)
Instructions: Customers can determine whether their NetScaler deployment meets this precondition by inspecting the configuration for DTLS-enabled virtual servers. A NetScaler Gateway is vulnerable if DTLS is not explicitly disabled, and other virtual servers are vulnerable if they are configured with type DTLS.
Relevant configuration patterns to check:
add vpn vserver vpn1 SSL 10.0.0.0 443 -Listenpolicy NONE This indicates DTLS is not explicitly disabled, so DTLS is enabled by default.
add vpn vserver vpn1 SSL 10.0.0.0 443 -dtls OFF -Listenpolicy NONE This indicates DTLS is explicitly disabled, so the precondition is not met.
add vpn vserver vs1 DTLS 10.11.1.1 443 This indicates DTLS is enabled.
add lb vserver vd_dtls DTLS 10.146.111.74 443 -persistenceType NONE -cltTimeout 120 This indicates DTLS is enabled.
CVE-2026-88773 Precondition: HTTP Configuration enabled on NetScaler ADC or NetScaler Gateway
Instructions: Customers can determine whether their NetScaler deployment meets this precondition if Load Balancing, Content Switching, VPN, or Authentication virtual servers of type HTTP or SSL are configured on NetScaler ADC or NetScaler Gateway.
add lb vserver <vserver-name> <HTTP or SSL>
add cs vserver <vserver-name> <HTTP or SSL>
add vpn vserver <vserver-name> <HTTP or SSL>
add authentication vserver <vserver-name> <HTTP or SSL>
CVE-2026-88774 Precondition: Any policy expression configured with HTTP URL based expression
Instructions: Customers can determine whether their NetScaler deployment meets this precondition if Load Balancing, Content Switching, VPN, or Authentication virtual servers of type HTTP or SSL are configured on NetScaler ADC or NetScaler Gateway.
add lb vserver <vserver-name> <HTTP or SSL>
add cs vserver <vserver-name> <HTTP or SSL>
add vpn vserver <vserver-name> <HTTP or SSL>
add authentication vserver <vserver-name> <HTTP or SSL>
CVE-2026-88775 Precondition: NetScaler ADC or NetScaler Gateway configured as either:
Instructions: Customers can determine whether their NetScaler deployment meets the precondition by inspecting their NetScaler configuration for entries matching either of the following regular expressions:
CVE-2026-88776 Preconditions: Configured as a Load Balancing (LB) virtual server of type Oracle on NetScaler ADC or NetScaler Gateway
Instructions: Customers can determine whether their NetScaler deployment meets this precondition by inspecting their NetScaler configuration for entries matching the following regular expression:
add lb vserver.*ORACLE.*
CVE-2026-88777 Preconditions: Configured as an LB/CS or CGNAT-LSN/NAT64 device with a non-HTTP L7 protocol feature enabled on NetScaler ADC or NetScaler Gateway
Instructions: Customers can determine whether their NetScaler deployment meets this precondition by inspecting their NetScaler configuration, such as /nsconfig/ns.conf or the output of show ns runningConfig, for entries matching any of the following case-insensitive regular-expression patterns. These patterns are intended for configuration-text search and are not NetScaler CLI commands.
grep -iE '' /nsconfig/ns.conf
A match against any pattern below indicates that the precondition may be met. Text after # is explanatory and is not part of the pattern.
FTP over LB / CS:
add (lb|cs) vserver .* FTP
add service .* FTP
FTP over LSN/CGNAT — FTP ALG is enabled by default unless explicitly disabled:
add lsn group .*
set lsn group .* -ftp DISABLED # explicitly disabled; if this line is absent, FTP ALG is treated as enabled, and the appliance is vulnerable
FTP via non-HTTP health monitor
add lb monitor .* FTP
add lb monitor .* FTP-EXTENDED
RTSP over LSN/CGNAT
set lsn group .* -rtspalg ENABLED
DNS64
add lb vserver .* DNS .* -dns64 ENABLED
add dns policy64 # (must be bound to a DNS vserver to be vulnerable)
NAT64
add nat64
CVE-2026-88778 Preconditions: TCP Configuration enabled on NetScaler ADC or NetScaler Gateway
Instructions: Customers can determine whether their NetScaler deployment meets the precondition by verifying that both of the following conditions are true:
At least one virtual server is configured with one of the following types: HTTP, SSL, SSL_BRIDGE, TCP, SSL_TCP, FTP, NNTP, RTSP, RDP, DNS_TCP, DOT, SIP_TCP, SIP_SSL, DIAMETER, SSL_DIAMETER, MYSQL, MSSQL, ORACLE, SMPP, MQTT, MQTT_TLS, MONGO, MONGO_TLS, PROXY, SSL_PROXY, USER_TCP, USER_SSL_TCP
AND
The following command returns: Enhanced ISN Generation: DISABLED:
show ns tcpparam | grep "Enhanced ISN Generation"
Acknowledgement
We acknowledge Michael Tucker, Chew Keong Tan and Alex Bernier of the JPMorgan Chase XOR Team, and Maxim Suhanov for working with us to protect our customers
Additional information / Reference
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
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.
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).
ICA Session launches may fail with reason «Licensing» in Citrix Director after the controller has entered an emergency license caching mode but is still within grace period.
Event ID 1163 from Citrix Broker Service reporting «No connection license available» , indicating launch failures is reported in the DDC application event logs.
Follow the below steps to identify if you are hitting this known issue.
1. Log into Citrix Director and view trends for connection failures. If you see the Failure Type as «No License Available» and Failure reason «Licensing»
Associated User
Failure Type
Failure Reason
Failure Time
Launch Time
Endpoint IP
Receiver Version
Machine Name
VDA Version
Delivery Group
xxx
No License Available
Licensing
4/2/2026 6:42
4/2/2026 6:41
10.6.1.176
n/a
yyy
xxxx
zzz
2. Check the Application event logs on the Delivery controller and filter the event ID’s 1154,503,504,1163,1156 with Event Sources Citrix Broker Service, Citrix High Availability Service, Citrix ConfigSync Service as shown below. If a Citrix Site has multiple DD’s then the event sequence may be seen on one or more DDC’s that exposed this behaviour with its interaction with its Citrix High Availability Service.
3. Check if the events are logged in below sequence.
Note:
During this process, Event IDs 503 and 504 from the Config Sync Service may or may not be observed.
The Config Sync Service can increase the likelihood of the issue occurring; however, the Citrix High Availability Service may independently detect the end of the grace period before the Citrix Broker Service. This timing difference can result in a race condition.
The key here is that Citrix High Availability Service reports that the controller is no longer in an emergency license caching mode with event ID 1156 before Citrix broker service reports the same with event ID 1156.
1. Event ID 1154 from Citrix Broker Service indicating the controller has entered an emergency license caching mode
2. Event ID 1154 from Citrix High Availability Service indicating the controller has entered an emergency license caching mode
3. Event ID 503,504 from Citrix ConfigSync Service for receiving and importing the updated configuration
4. Event ID 1156from Citrix High Availability Service reporting «The Citrix Broker Service is successfully communicating with the license server ‚xxx‘. This controller is no longer in an emergency license caching mode.»
5. Event ID 1163 from Citrix Broker Service reporting «No connection license available» , indicating launch failures.
6. Event ID 1156 from Citrix Broker Service reporting «The Citrix Broker Service is successfully communicating with the license server ‚xxx‘. This controller is no longer in an emergency license caching mode.»
Here is the detailed event Log output for each of the event ID’s listed above:
Log Name: Application Source: Citrix Broker Service Date: 02-04-2026 06:43:44 Event ID: 1154 Task Category: None Level: Warning Keywords: User: NETWORK SERVICE Computer: yyy Description: This controller has entered an emergency license caching mode because it could not contact the license server ‚xxx‘.
You have 716 hour(s) remaining before this controller stops providing desktop and application sessions.
Log Name: Application Source: Citrix High Availability Service Date: 02-04-2026 06:43:49 Event ID: 1154 Task Category: None Level: Warning Keywords: User: NETWORK SERVICE Computer: yyy Description: This controller has entered an emergency license caching mode because it could not contact the license server ‚xxx‘.
You have 720 hour(s) remaining before this controller stops providing desktop and application sessions.
Log Name: Application Source: Citrix ConfigSync Service Date: 02-04-2026 06:49:08 Event ID: 503 Task Category: None Level: Information Keywords: Classic User: N/A Computer: yyy Description: The Citrix Config Sync Service received an updated configuration.
Log Name: Application Source: Citrix ConfigSync Service Date: 02-04-2026 06:50:44 Event ID: 504 Task Category: None Level: Information Keywords: Classic User: N/A Computer: yyy Description: The Citrix Config Sync Service imported an updated configuration.
Log Name: Application Source: Citrix High Availability Service Date: 02-04-2026 06:50:51 Event ID: 1156 Task Category: None Level: Information Keywords: User: NETWORK SERVICE Computer: yyy Description: The Citrix Broker Service is successfully communicating with the license server ‚xxx‘. This controller is no longer in an emergency license caching mode.
Log Name: Application Source: Citrix Broker Service Date: 02-04-2026 06:51:16 Event ID: 1163 Task Category: None Level: Warning Keywords: User: NETWORK SERVICE Computer: yyy Description: No connection license available. To resolve, free licenses by closing sessions that are not needed, or add more licenses.
Details: License Server Address: ‚xxx‘ License Server Port: ‚27000‘ Site License Model: ‚Concurrent‘ Site Edition: ‚PLT‘ ProductID: ‚XDT‘ User:zzz Client ID: ‚FF01753A‘ Session Support: ‚MultiSession‘
Log Name: Application Source: Citrix Broker Service Date: 02-04-2026 06:58:34 Event ID: 1156 Task Category: None Level: Information Keywords: User: NETWORK SERVICE Computer: yyy Description: The Citrix Broker Service is successfully communicating with the license server ‚xxx‘. This controller is no longer in an emergency license caching mode.
Problem Cause
Issue identified in the product.
Resolution
Refer to the below links to access the Hotfixes for different LAS compatible Delivery Controller versions:
The below workaround can be followed if you are unable to implement the Hotfixfix for any reason on the delivery controllers.
Note:
This workaround should be applied only after the issue occurs. It ensures that sessions launch successfully when the controller enters emergency license caching mode; however, a side effect is that Local Host Cache (LHC) will be disabled.
Once connectivity is restored and the primary Broker is confirmed to be out of the grace period (for example, by verifying Event ID 1156 in the Citrix Broker Service logs), you can restart the Citrix Config Sync Service and the Citrix High Availability Service to restore LHC functionality. However, If the controller enters emergency license caching mode again, these steps will need to be repeated.
Follow the below steps on one of the Delivery Controller:
Step 1: Stop these services:
Citrix ConfigSync Service
Citrix High Availability Service
Citrix Broker Service
In powershell, run:
Stop-Service CitrixConfigSyncService
Stop-Service CitrixHighAvailabilityService
Stop-Service CitrixBrokerService
Step 2: Start Citrix Broker Service In powershell, run: Start-Service CitrixBrokerService
Step 3: Wait 5-10min. Run powershell to check connection: Test-BrokerLicenseServer -ComputerName <license server address> -Port 8083 –CheckLasPE $true
If the result is Compatible, it means the connection to LAS is ok. If the result is NotCompatible/Inaccessible/InternalError, it means the connection to LAS is down.
Step 4: In event log, confirm Citrix Broker Service reports 1154 event again:
Summary
ICA Session launches may fail with reason «Licensing» in Citrix Director after the controller has entered an emergency license caching mode but is still within grace period.
Event ID 1163 from Citrix Broker Service reporting «No connection license available» , indicating launch failures is reported in the DDC application event logs.
Caution! This release may require you to edit the registry. Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.
This Update is for Version 2511 of the Citrix Virtual Apps and Desktops. Any known issues in Version 2511, except for the specific issues resolved in this release, still apply.
Where to Find Documentation
This document describes the issue(s) resolved by this Update and includes installation instructions. For additional product information, including supported operating systems and system requirements, see Citrix Virtual Apps and Desktops 2511 on the Citrix Product Documentation site.
Symptoms
ICA Session launches may fail with reason «Licensing» in Citrix Director after the controller has entered an emergency license caching mode but is still within grace period.
or
When LAS connection is lost, end users fail to launch desktop or application sessions with error in event log with event id 1163
New Fixes in This Release
This release includes bug fixes for the License Activation Service (LAS) to improve high-availability (HA) performance and ensure accurate licensing status reporting, and to address the symptoms mentioned above.
Key Improvements
Race condition during licensing state transitions could lead to incorrect license caching mode period calculations. This prevents session launches (CVADHELP-31920).
Fixes from Replaced Updates
No Updates were replaced by this release.
Installing and Uninstalling this Release
Notes:
Maintenance Window Recommendation: Citrix recommends scheduling a maintenance window to minimize user impact during the update process.
Caution: Citrix recommends that you back up your database before installing this hotfix. Doing so allows you to manually restore your database to the backed-up version. Any changes made between backup and restore will be lost. For information about backing up and restoring your database, see: https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/upgrade-migrate
To Install This Update:
Use the following steps to apply this update:
Stop the Citrix Broker Service and Citrix High Availability Service.
Rename the files NetLicwrapper.dll, Citrix.Licensing.LasPolEng.dll under C:\Program Files\Citrix\Broker\Service to NetLicwrapper_Backup.dll, Citrix.Licensing.LasPolEng_Backup.dll.
Extract the downloaded ZIP file and copy the extracted files to C:\Program Files\Citrix\Broker\Service.
Restart the Citrix Broker Service and Citrix High Availability Service.
To Uninstall This Update
Use the following steps to remove this update:
Stop the Citrix Broker Service and Citrix High Availability Service.
Rename the files NetLicwrapper.dll, Citrix.Licensing.LasPolEng.dll under C:\Program Files\Citrix\Broker\Service to NetLicwrapper_Update1.dll, Citrix.Licensing.LasPolEng_Update1.dll.
Rename the files NetLicwrapper_Backup.dll, Citrix.Licensing.LasPolEng_Backup.dll under C:\Program Files\Citrix\Broker\Service to NetLicwrapper.dll, Citrix.Licensing.LasPolEng.dll.
Restart the Citrix Broker Service and Citrix High Availability Service.
Attention! Please note the following regarding to this update:
Netscaler customers who are not yet using Flex licensing (CITRIX HMC) or Fixed Term licenses must download the installed license file again from the www.citrix.com portal (License) with the correct MAC address and replace it on the Netscaler. These newly created license files will then only be valid until April 2026. If the file is not replaced, the Netscaler will start up with a freemium license after a reboot! AXACOM AG recommends installing this patch (medium with a score of 5.9) only when the Netscaler can be converted to the new LAS licensing.
License Activation Service
Important:
File-based licensing system (also referred to as manually managed entitlements), traditionally used for activating various on-premises components, will be End of Life (EOL) on April 15, 2026. License Activation Service (LAS) is the next generation technology for product activations across the suite of Citrix products. LAS will be the only way to activate and license NetScaler instances after April 15, 2026, supporting NetScaler Flexed licenses (CPL/UHMC), legacy NetScaler Pooled licenses, and NetScaler Fixed term Bandwidth licenses. To remain supported, your NetScaler and NetScaler Console deployments must be on a LAS compatible version.
The minimum required NetScaler® versions that are LAS compatible are:
NetScaler Console Service: Supported from early September 2025
NetScaler Console on-prem: 14.1-51.83Note: LAS support for Console on-prem is from release 14.1-51.83 onwards. However, file-based licensing is deprecated from Console on-prem releases 14.1-51.83 onwards and 13.1-60.26 onwards, and goes EOL on April 15th, 2026. That is, even if you upgrade to Console on-prem release 14.1-51.83 or release 13.1-60.26 or later, you can continue using file-based licensing. However you must upgrade to Console on-prem release 14.1-51.83 or later, and switch to LAS before 15th April 2026 because file-based licensing reaches EOL.
All the other forms of legacy NetScaler licenses such as Pooled vCPU, CICO, perpetual will not be supported with LAS. NetScaler instances leveraging perpetual licenses without an active maintenance will become unlicensed upon upgrade to the above mentioned software versions.
LAS based licenses may not be available to customers where prohibited by law or regulations.
If you have questions or concerns, contact Customer Care. Citrix® may limit or suspend your Citrix Maintenance for non-compliance with these requirements without liability in addition to any other remedies Citrix may have at law or equity. These requirements don’t apply where prohibited by law or regulation.
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.
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 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 .*
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 .*
