CVE-2026-19490
CVE-2026-19490 is a security flaw in Citrix NetScaler, the gateway companies use to let staff reach internal apps from outside. Attackers can get into Citrix NetScaler without a valid password. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 9 Sep 2026.[1]
Citrix NetScaler is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Citrix has published a fix or advice.
Description
CISA calls it an authentication bypass using an alternate path or channel in Citrix NetScaler. In its words: “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.”[1]
The underlying weakness is authentication bypass (CWE-288), in MITRE’s list of common software weaknesses.[2]
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Citrix’s advisory has them[3]. CISA names the product as Citrix NetScaler.
Most families won’t have Citrix NetScaler; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 9 Sep 2026, 21 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 12 Sep 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 33%. That’s in the top 2% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Citrix has published a fix or advice.[3] CISA’s 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).”[1]
- Check whether you use it.Citrix NetScaler is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 12 Sep 2026 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 33%.[4] |
See also
Other Citrix NetScaler flaws
- CVE-2026-88779: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88772: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88771: improper input validation ·
- CVE-2026-3055: out-of-bounds read ·
- CVE-2025-7775: memory overflow ·
Other Citrix flaws
- CVE-2026-8452, Citrix NetScaler ADC and NetScaler Gateway: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2024-8069, Citrix Session Recording: deserialization of untrusted data ·
- CVE-2024-8068, Citrix Session Recording: improper privilege management ·
- CVE-2025-5777, Citrix NetScaler ADC and Gateway: out-of-bounds read ·
- CVE-2025-6543, Citrix NetScaler ADC and Gateway: buffer overflow ·
Other authentication bypass flaws
- CVE-2026-20079, Cisco Secure Firewall Management Center (FMC) and Security Cloud Control (SCC) Firewall Management: firewall management center authentication bypass using an alternate path or channel ·
- CVE-2026-18556, N-able N-central: authentication bypass using an alternate path or channel ·
- CVE-2026-18577, N-able N-central: authentication bypass using an alternate path or channel ·
- CVE-2026-1603, Ivanti Endpoint Manager (EPM): authentication bypass ·
- CVE-2026-24858, Fortinet products: authentication bypass using an alternate path or channel ·
Added the same day
- CVE-2026-87491, Chrome and other Chromium browsers: out of bounds write ·
- CVE-2026-20079, Cisco Secure Firewall Management Center (FMC) and Security Cloud Control (SCC) Firewall Management: firewall management center authentication bypass using an alternate path or channel ·
- CVE-2025-25249, Fortinet products: heap-based buffer overflow ·
Every Citrix flaw on CISA’s list · Everything added in September 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Citrix NetScaler Authentication Bypass Using an Alternate Path or Channel Vulnerability”. Known Exploited Vulnerabilities Catalog, added 9 Sep 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-19490 Detail”. National Vulnerability Database, published 19 Aug 2026.
- ^ Citrix. Advisories and fixes: support.citrix.com, support.citrix.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.327, percentile 98.3, 31 Oct 2026.
- CVE Program. “CVE-2026-19490”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.