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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.

Citrix urges customers to fix critical NetScaler authentication bypass (CVE-2026-19490)

Citrix patched a critical authentication bypass, CVE-2026-19490, in NetScaler Gateway and NetScaler ADC, urging customers to upgrade immediately.

Citrix has patched two flaws in NetScaler ADC and NetScaler Gateway. CVE-2026-19490 is a critical authentication bypass (CVSS v4.0 9.3) that works when the appliance is configured as an SSL VPN, ICA Proxy, CVPN, RDP Proxy Gateway or AAA virtual server, with additional conditions depending on firmware and SAML configuration. A second flaw, CVE-2026-19489 (CVSS 8.8), is a memory overflow that can cause denial of service when SIP ALG is enabled on LSN setups. Rapid7 had not observed exploitation as of August 19, 2026, but urged emergency patching; a signature-based mitigation is available via NetScaler Console.

AL26-019 - Vulnerabilities impacting Citrix NetScaler ADC and NetScaler Gateway - CVE-2026-19490 and CVE-2026-19489

Canadian Cyber Centre alerts on Citrix NetScaler ADC/Gateway flaws CVE-2026-19490 (authentication bypass) and CVE-2026-19489 (buffer overflow), urging emergency patching.

The Canadian Centre for Cyber Security issued alert AL26-019 covering two Citrix NetScaler vulnerabilities disclosed in a vendor advisory on August 19, 2026. CVE-2026-19490 (CWE-288) allows a remote unauthenticated attacker to bypass authentication on appliances configured as a Gateway for SSL VPN, ICA Proxy, CVPN, RDP Proxy, or as an AAA virtual server. CVE-2026-19489 (CWE-120) is a classic buffer overflow that may cause memory overflow, unpredictable behavior, or denial-of-service conditions. Affected appliances are vulnerable when configured as a SAML IdP; fixed versions include 14.1-73.32, 13.1-63.21, and 13.1-37.277 for FIPS.

Citrix security advisory (AV26-645) – Update 3

Canada's Cyber Centre updates Citrix advisory as CVE-2026-8451 and CVE-2026-8452 in NetScaler ADC/Gateway are confirmed exploited in the wild.

The Canadian Centre for Cyber Security updated advisory AV26-645 on August 26, 2026, covering critical vulnerabilities in Citrix NetScaler ADC and Gateway (versions 14.1 before 14.1-72.61 and 13.1 before 13.1-63.18, plus FIPS builds). Open-source reporting indicates CVE-2026-8451 and CVE-2026-8452 are being exploited in the wild. Update 3 references related CISA action, and patched builds were released starting June 30, 2026.

CISA Warns of Citrix NetScaler Authentication Bypass Vulnerability Exploited in Attacks

CISA adds exploited Citrix NetScaler authentication bypass CVE-2026-19490 to the KEV catalog; federal agencies must patch by September 12.

CISA added CVE-2026-19490, a CWE-288 authentication bypass affecting NetScaler ADC and Gateway deployments configured as AAA virtual servers or Gateway services (including SSL VPN, ICA Proxy, and RDP Proxy), to the Known Exploited Vulnerabilities catalog. Citrix released fixes on August 19, 2026; honeypots recorded 56 attack attempts between September 3 and 8 after a public PoC, though no confirmed production compromises have been reported. Affected builds include 14.1 before 14.1-73.32 and 13.1 before 13.1-63.21; newer installations require SAML IdP configuration to be exposed.

Cyber Security Newsupdated · 5d agofirst · 6d agoExploit / PoC in the wild 5 sourcesCVE-2026-19490