{"id":"CVE-2026-19490","kind":"vulnerability","aliases":["CVE-2026-19490"],"related":[],"title":"Vulnerability in NetScaler ADC and NetScaler Gateway","description":"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.\n\nCISA 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.","summary":"Authentication bypass (CWE-288, CVSS v4 9.3) in customer-managed NetScaler ADC and Gateway. An unauthenticated attacker can skip login when the appliance is a Gateway (SSL VPN, ICA Proxy, CVPN, RDP Proxy) or an AAA vserver. Under 14.1-43.56+ and 13.1-61.28+ (including 14.1 FIPS 14.1-66.68+), it applies only if a SAML action is also configured. Exploited in the wild and in CISA KEV. Fixed 2026-08-19 in the same release as CVE-2026-19489, a SIP ALG buffer overflow.","severity":"critical","cvss":9.8,"epss":null,"exploited":true,"exploited_at":"2026-09-09T00:00:00+00:00","products":[{"name":"Citrix NetScaler","fixed":[],"affected":"","ecosystem":"vendor"},{"name":"NetScaler ADC","fixed":["14.1-73.32","13.1-63.21","14.1-73.32 FIPS","13.1-37.277"],"affected":"14.1 < 14.1-73.32; 13.1 < 13.1-63.21; 14.1-FIPS < 14.1-73.32 FIPS; 13.1-FIPS/NDcPP < 13.1-37.277","ecosystem":"vendor"},{"name":"NetScaler Gateway","fixed":["14.1-73.32","13.1-63.21"],"affected":"14.1 < 14.1-73.32; 13.1 < 13.1-63.21","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["13.1-37.277"],"affected":">= 13.1, < 13.1-37.277","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["13.1-63.21"],"affected":">= 13.1, < 13.1-63.21","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["14.1-73.32"],"affected":">= 14.1, < 14.1-73.32","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":[],"affected":">= 14.1-66.68, <= 14.1-73.32","ecosystem":"vendor"},{"name":"citrix netscaler gateway","fixed":["13.1-63.21"],"affected":">= 13.1, < 13.1-63.21","ecosystem":"vendor"},{"name":"citrix netscaler gateway","fixed":["14.1-73.32"],"affected":">= 14.1, < 14.1-73.32","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["authentication-bypass","citrix","exploited","infrastructure","netscaler","netscaler-adc","netscaler-gateway","poc-public","self-hosted","vpn"],"not_affected_if":["managed-hosting","no-gateway-or-aaa-vserver","no-saml-action-on-newer-builds","not-aaa-or-gateway-config"],"how_to_check":"On the appliance, search the running config for 'add authentication samlAction', 'add authentication vserver' and 'add vpn vserver'. Exposed if a Gateway or AAA vserver exists on a vulnerable build. On 14.1-43.56+ and 13.1-61.28+, a SAML action must also be present. Check the build with 'show version'. Because it is exploited, also review for unexpected sessions and run CISA's forensics triage.","fix":"Upgrade to 14.1-73.32 or later, 13.1-63.21 or later, 14.1-73.32 FIPS or later, or 13.1-37.277 or later for 13.1-FIPS and NDcPP. Secure Private Access Hybrid deployments using NetScaler instances need the same upgrade. Citrix-managed cloud and Adaptive Authentication are patched by Citrix. No workaround is listed in the bulletin.","status":"open","published_at":"2026-08-19T13:17:45+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T20:31:36+00:00","updated_at":"2026-10-24T00:09:50+00:00","category":"infrastructure","confidence":0.9,"triage":{"at":"2026-10-23T20:31:36Z","model":"claude-haiku-5-5","output":{"fix":"Apply the vendor mitigations or patch per Citrix guidance; CISA's required action also says to discontinue use of the product if mitigations are unavailable. Exact fixed versions: unknown.","summary":"Citrix NetScaler ADC and NetScaler Gateway have an authentication bypass flaw in their alternate path or channel handling, reachable without credentials when the appliance runs as an AAA virtual server or as a Gateway (SSL VPN, ICA Proxy, CVPN, or RDP Proxy). An unauthenticated remote attacker may be able to skip login and reach protected resources, and CISA reports it as exploited in the wild.","category":"infrastructure","who_cares":["citrix","netscaler","netscaler-gateway","self-hosted","vpn"],"confidence":0.7,"analyst_note":"Get affected and fixed NetScaler versions, the Citrix advisory, and a configuration or log check for auth bypass from the Citrix security bulletin and the CISA KEV entry.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["not-aaa-or-gateway-config","managed-hosting"],"severity_if_unknown":"critical"},"cost_usd":0.000436,"input_tokens":2286,"output_tokens":414,"severity_before":"unknown"},"analyst_status":"done","analyst_note":"Get affected and fixed NetScaler versions, the Citrix advisory, and a configuration or log check for auth bypass from the Citrix security bulletin and the CISA KEV entry.","search":"'-04':219C,245C,276C '-08':135B '-19':136B '-19489':144B '-19490':10A,13A '-2026':9A,12A,143B '-288':69B '-43.56':106B '-61.28':109B '-66.68':114B '13.1':108B '14.1':105B,111B,113B '2026':134B '26':218C,244C,275C '9.3':72B 'aaa':102B,176C 'abl':198C 'accord':208C 'action':121B,204C 'actor':195C 'adc':4A,17A,55B,78B,152C 'adher':272C 'alg':147B 'also':123B 'altern':164C 'appli':116B,205C 'applianc':89B,171C 'applic':242C 'application':22A,27A,32A,37A 'asset':266C 'attack':83B 'authent':47B,66B,159C,201C 'authentication-bypass':46B,158C 'base':223C 'bod':217C,243C,274C 'buffer':148B 'bypass':48B,67B,160C,200C 'channel':167C 'cisa':131B,202C,215C,232C 'citrix':14A,20A,25A,30A,35A,40A,43A,49B,150C 'cloud':248C 'complianc':213C 'configur':124B,173C 'contain':156C 'controller':24A,29A,34A,39A 'custom':75B 'customer-manag':74B 'cve':8A,11A,142B 'cvpn':97B,187C 'cvss':70B 'cwe':68B 'delivery':23A,28A,33A,38A 'discontinu':251C 'ensur':212C,271C 'evalu':264C 'exploit':50B,125B 'exposur':269C 'fip':112B 'fix':133B 'follow':241C 'forens':234C 'gateway':7A,19A,42A,45A,58B,80B,92B,155C,182C 'guidanc':230C,246C 'guidelin':278C 'host':64B 'ica':95B,185C 'includ':110B 'infrastructur':51B 'instruct':211C 'internet':268C 'involv':162C 'kev':132B 'login':86B 'manag':76B 'may':196C 'mitig':206C,257C 'netscal':3A,6A,52B,54B,57B,77B,151C,154C,170C 'netscaler':15A,16A,18A,21A,26A,31A,36A,41A,44A 'netscaler-adc':53B 'netscaler-gateway':56B 'note':229C,240C 'overflow':149B 'patch':277C 'path':165C 'poc':60B 'poc-publ':59B 'priorit':220C 'product':255C 'proxi':96B,99B,186C,190C 'public':61B 'rdp':98B,189C 'releas':140B 'remot':193C 'requir':203C,236C 'respons':262C 'risk':225C 'saml':120B 'secur':221C 'see':226C,237C 'self':63B 'self-host':62B 'server':178C 'servic':249C 'sip':146B 'skip':85B 'ssl':93B,183C 'stakehold':260C 'threat':194C 'triag':235C 'unauthent':82B,192C 'unavail':259C 'updat':222C 'url':227C,238C 'use':252C 'v4':71B 'vendor':210C 'virtual':177C 'vpn':65B,94B,184C 'vserver':103B 'vulner':1A,161C 'wild':128B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2026-08-19T13:17:45+00:00","kev":{"dateAdded":"2026-09-09","dueDate":"2026-09-12","requiredAction":"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.","knownRansomwareCampaignUse":"Unknown"},"cvss_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","cvss_by":"50a63c94-1ea7-4568-8c11-eb79e7c5a2b5","poc_count":1,"sources":[{"source":"kev","external_id":"CVE-2026-19490","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2026-19490","severity":null,"published_at":"2026-09-09T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:51+00:00","fetched_at":"2026-10-25T17:39:54+00:00","note":null},{"source":"analyst","external_id":"CVE-2026-19490:88","url":null,"severity":null,"published_at":"2026-10-23T21:29:00+00:00","modified_at":"2026-10-23T21:29:00+00:00","first_seen_at":"2026-10-23T21:29:00+00:00","fetched_at":"2026-10-23T21:29:00+00:00","note":"Read Citrix bulletin CTX696939 (2026-08-19): CVSS v4 9.3, fixed builds and precondition checks taken from it. Exploitation per CISA KEV (added 2026-09-09) and CSA Singapore, which also reports a public PoC, but I found no PoC link so none is attached. Reporter credit: Samarth Vashisht (JPMorgan Chase)."},{"source":"nvd","external_id":"CVE-2026-19490","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-19490","severity":null,"published_at":"2026-08-19T13:17:45+00:00","modified_at":"2026-10-07T19:17:36+00:00","first_seen_at":"2026-10-23T23:44:52+00:00","fetched_at":"2026-10-23T23:44:52+00:00","note":null},{"source":"github-poc","external_id":"CompleteTech-LLC/netscaler-cve-2026-19490-check","url":"https://github.com/CompleteTech-LLC/netscaler-cve-2026-19490-check","severity":null,"published_at":"2026-10-23T23:41:11+00:00","modified_at":null,"first_seen_at":"2026-10-23T23:55:02+00:00","fetched_at":"2026-10-23T23:55:02+00:00","note":null}],"documents":[{"id":1030,"url":"https://support.citrix.com/external/article/CTX696939/netscaler-adc-and-netscaler-gateway-secu.html","title":"Citrix bulletin CTX696939 (CVE-2026-19489, CVE-2026-19490)","kind":"vendor","source":"analyst","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":null},{"id":1034,"url":"https://www.csa.gov.sg/alerts-and-advisories/alerts/al-2026-115/","title":"CSA Singapore AL-2026-115: active exploitation, public PoC reported","kind":"advisory","source":"analyst","text":null,"published_at":null,"relation":"mentions","confidence":null,"note":null},{"id":1035,"url":"https://www.bleepingcomputer.com/news/security/citrix-urges-admins-to-patch-new-netscaler-flaws-as-soon-as-possible/","title":"BleepingComputer: Citrix urges admins to patch new NetScaler flaws","kind":"blog","source":"analyst","text":null,"published_at":null,"relation":"describes","confidence":null,"note":null},{"id":2252,"url":"https://github.com/CompleteTech-LLC/netscaler-cve-2026-19490-check","title":"CompleteTech-LLC/netscaler-cve-2026-19490-check","kind":"poc","source":"github","text":"Standalone defensive checker project for CVE-2026-19490: Citrix NetScaler ADC / Gateway: Gateway / AAA alternate-path authentication bypass. One exploit per repository; implementation pending.\n\nstars 0","published_at":"2026-10-23T23:41:11+00:00","relation":"poc","confidence":null,"note":"0 stars"}],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}