Critical NetScaler Flaw Can Bypass Authentication on Certain Gateway and AAA Servers
Citrix patches critical NetScaler Gateway and AAA authentication bypass CVE-2026-19490 (CVSS 9.3) plus a SIP ALG memory overflow flaw; exploitation attempts observed.
Citrix fixed CVE-2026-19490 (CVSS 9.3), an authentication bypass affecting customer-managed NetScaler ADC and Gateway appliances configured as Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy) or AAA virtual servers, and CVE-2026-19489 (CVSS 8.8), a memory overflow causing DoS when SIP ALG is enabled in Large Scale NAT groups. Updates are available in versions 14.1-73.32, 13.1-63.21, and corresponding FIPS/NDcPP builds, while Citrix-managed cloud services were already patched. The flaws were reported by Samarth Vashisht of JPMorgan Chase's penetration-testing team, and Previdian later observed 10 exploitation attempts against CVE-2026-19490 from six unique IP addresses in Australia, Germany, Japan, and the US, with no confirmed compromise.
- CVE-2026-19490 bypass applies to Gateway or AAA vserver configurations; SAML action matters on newer builds.
- CVE-2026-19489 only triggers with SIP ALG enabled in LSN group configurations.
- NetScaler Console Global Deny Lists signatures can mitigate the authentication bypass.
- Previdian recorded 10 exploitation attempts from six IPs; no confirmed compromise.
- Vendors
- Citrix
- Organizations
- JPMorgan ChasePrevidian
- Countries
- AustraliaGermanyJapanUnited States
Vulnerabilities mentioned
All| CVE | Vulnerability | CVSS | EPSS | Signals | Published |
|---|---|---|---|---|---|
| CVE-2026-19489 | Unauthenticated Buffer Overflow in Citrix NetScaler ADC and NetScaler Gateway | 8.8 | <1% | ||
| CVE-2026-19490 | Remote Authentication Bypass in Citrix NetScaler ADC and NetScaler Gateway | 9.3 | 33% | KEVPoC | KEV |
| CVE-2026-8451 | Insufficient input validation in NetScaler ADC and NetScaler Gateway leading to memory overread if NetScaler ADC or NetScaler Gateway is configured as a SAML… | 8.8 | 16% |
From the original article
3 min read at thehackernews.com
Ravie Lakshmanan Aug 20, 2026 Network Security / Enterprise Security Citrix has released updates to address two security flaws impacting NetScaler ADC and NetScaler Gateway deployments, including a critical-severity authentication bypass vulnerability.
By @TheHackersNews · thehackernews.com
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