Citrix NetScaler Authentication Bypass Using an Alternate Path or Channel Vulnerability (CVE-2026-19490)
Severity: critical · Patch status: unknown · Since 2026-09-09 · CVE-2026-19490
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 added CVE-2026-19490 to its Known Exploited Vulnerabilities catalog on Sep 9, 2026, which means attackers are exploiting it in the wild.
What to do
- 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.
- US federal agencies must remediate by Sep 12, 2026 (BOD 22-01); treat that as the outer limit.
Sources
All live incidents on Threat Watch
