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CVE-2026-19490: Citrix NetScaler Authentication Bypass Using an Alternate Path or Channel Vulnerability

In short

Citrix NetScaler has a weakness classified as authentication bypass using an alternate path or channel (CWE-288). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-09-09. NVD lists CVSS 4.0 at 9.3 CRITICAL.

What it is

“Citrix NetScaler ADC and NetScaler Gateway contain an authentication-bypass vulnerability involving an alternate path or channel. When the NetScaler appliance is configured as an AAA virtual server or as a Gateway (SSL VPN, ICA Proxy, CVPN, or RDP Proxy), an unauthenticated remote threat actor may be able to bypass authentication.” — CISA KEV, retrieved 2026-11-01
“Vulnerability in NetScaler ADC and NetScaler Gateway. This issue affects ADC: from 14.1 through 73.32 and from 13.1 through 63.21; Gateway: from 14.1 through 73.32 and from 13.1 through 63.21.” — NVD, retrieved 2026-11-01

Who is affected

Citrix NetScaler. NVD lists the following versions as affected:

  • Citrix Netscaler Application Delivery Controller: from 13.1 inclusive, before 13.1-37.277
  • Citrix Netscaler Application Delivery Controller: from 13.1 inclusive, before 13.1-63.21
  • Citrix Netscaler Application Delivery Controller: from 14.1 inclusive, before 14.1-73.32
  • Citrix Netscaler Application Delivery Controller: from 14.1-66.68 inclusive, through 14.1-73.32
  • Citrix Netscaler Gateway: from 13.1 inclusive, before 13.1-63.21
  • Citrix Netscaler Gateway: from 14.1 inclusive, before 14.1-73.32

Exploitation status

CISA KEV added: 2026-09-09. Known ransomware campaign use: Not reported by CISA. Due date CISA set for US federal civilian agencies: 2026-09-12.

Scores

NVD CVSS 4.0: 9.3 CRITICAL; vector 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source 50a63c94-1ea7-4568-8c11-eb79e7c5a2b5.

EPSS by FIRST: 32.65%; percentile 98.34; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-288.

Timeline

Source events
DateEvent
2026-08-19T13:17:45.000NVD published
2026-09-09CISA KEV added
2026-09-12CISA KEV due
2026-10-26T13:10:00.140NVD last modified
2026-10-31FIRST EPSS score

CISA required action

“Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.” — CISA KEV

What to do

  • Confirm whether you run Citrix NetScaler and which version.
  • Apply the vendor update or mitigation in the advisory.
  • Follow CISA’s required action.
  • Review the vendor guidance on signs of compromise.
  • Track the fix through completion.

References

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.

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