CVE-2026-88778
citrix netscaler application delivery controller
Summary
Predictable exact value from previous values vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway. This issue affects ADC: before 14.1-73.37, before 13.1-64.23, before 14.1-73.37 FIPS, and before 13.1.37.279 FIPS and NDcPP; Gateway: before 14.1-73.37 and before 13.1-64.23.
Published 2026-09-27 · first seen here 2026-10-10
Analysis & write-ups
- Defending Against Active Exploitation of Citrix NetScaler ADC and Gateway Appliances · Google Threat Intelligence
- Zero-Day Exploitation of Citrix NetScaler ADC and Gateway: CVE-2026-88771 and CVE-2026-88772 · Rapid7
- Here We Go Again (Citrix NetScaler DTLS Preauth Memory Overflow CVE-2026-88772) · watchTowr Labs
- Oh Look, The Foot Gun Went Off Again (Citrix NetScaler PreAuth Command Injection CVE-2026-88771) · watchTowr Labs
Where it shows in your logs
Edge or network appliance (firewall, VPN, gateway) · Authentication bypass or missing authorisation high confidence
Appliances usually run no EDR, so device logs, firewall flow logs and the vendor's integrity checker are often the only evidence. Get the logs off the box: attackers often wipe local logs.
What to look for
- Admin or API actions with no successful login before them in the same session
- New admin accounts, API keys or tokens created shortly after unusual requests
- Requests to admin or API endpoints from internet IPs
- Configuration changes, new local admin accounts or new VPN users on the appliance
- Admin or VPN logins from unfamiliar IPs, especially VPS or hosting providers
- New outbound connections from the appliance's own IP (it should rarely start connections)
- Gaps in the appliance's logs, unexpected reboots or crashes, or logs that were cleared
Data sources
Appliance system and admin logs · ATT&CK DS0015 Application Log Content
- Sentinel
CommonSecurityLog (CEF from Fortinet, Palo Alto, Check Point, Cisco)Syslog- Splunk
Vendor add-ons: fortigate_event, pan:system, pan:config, cisco:asa, citrix:netscaler:syslog, f5:bigip:syslogChange.All_Changes- CrowdStrike
Falcon Next-Gen SIEM: third-party firewall / VPN connectors
Authentication and sessions · ATT&CK DS0028 Logon Session Creation / DS0002 User Account Authentication
- Sentinel
SigninLogsSecurityEvent (4624, 4625, 4648)DeviceLogonEventsIdentityLogonEvents_Im_Authentication- Splunk
Authentication.Authenticationpan:globalprotectVPN sourcetypes- CrowdStrike
UserLogonUserLogonFailed2Falcon Identity Protection events
Network connections · ATT&CK DS0029 Network Connection Creation / Network Traffic Flow
- Sentinel
DeviceNetworkEventsCommonSecurityLog (firewall)_Im_NetworkSession- Splunk
Network_Traffic.All_TrafficFirewall sourcetypes (pan:traffic, fortigate_traffic, cisco:asa)- CrowdStrike
NetworkConnectIP4NetworkReceiveAcceptIP4NetworkConnectIP6
Account and group changes · ATT&CK DS0002 User Account Creation / Modification
- Sentinel
SecurityEvent (4720, 4728, 4732, 4756)AuditLogsIdentityDirectoryEvents- Splunk
Change.All_Changes (Account_Management)WinEventLog:Security (4720, 4732)- CrowdStrike
UserAccountCreatedUserAccountAddedToGroup
A generic baseline worked out from the product type and weakness (CWE-342), not a detection. Check table and field names against your environment. Hunt queries for Sigma, Splunk, Sentinel and CrowdStrike are coming.