Article Id : CTX697096
Last Modified Date : 09-27-2026 15:25
Created Date : 09-27-2026 15:22
Article Record Type : Security BulletinSeverity :
Critical
Summary
Severity – Critical
Description of Problem
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
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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
NetScaler deployments impacted by CVE-2026-88778 should apply the TCP configuration change as mentioned in https://docs.netscaler.com/en-us/citrix-adc/current-release/system/tcp-configurations.html#enhanced-isn-generation
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:
• Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy)
• AAA virtual server
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:
- Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy):
add vpn vserver .* - AAA virtual server:
add authentication vserver .*
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 .* FTPadd 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 .* FTPadd lb monitor .* FTP-EXTENDED
RTSP over LSN/CGNAT
set lsn group .* -rtspalg ENABLED
DNS64
add lb vserver .* DNS .* -dns64 ENABLEDadd 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
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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