CVE-2019-19781
CVE-2019-19781 is a security flaw in Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance, the gateway companies use to let staff reach internal apps from outside. Attackers can run their own code on Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 3 Nov 2021, and says ransomware gangs have used it.[1]
Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance 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 ADC, gateway, and SD-WAN WANOP appliance code execution in Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance. In its words: “Citrix ADC, Citrix Gateway, and multiple Citrix SD-WAN WANOP appliance models contain an unspecified vulnerability that could allow an unauthenticated attacker to perform code execution.”[1]
The underlying weakness is path traversal (CWE-22), 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 Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance.
Most families won’t have Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 3 Nov 2021, 677 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 3 May 2022 to fix it.[1] CISA says ransomware gangs have used it.
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 over 99%. That’s in the top 1% 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 updates per vendor instructions.”[1]
- Check whether you use it.Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance 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 3 May 2022 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, noting that ransomware gangs have used it.[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 over 99%.[4] |
See also
Other Citrix Application Delivery Controller (ADC), Gateway, and SD-WAN WANOP Appliance flaws
- CVE-2020-8196: ADC, gateway, and SD-WAN WANOP appliance information disclosure ·
- CVE-2020-8195: ADC, gateway, and SD-WAN WANOP appliance information disclosure ·
- CVE-2020-8193: ADC, gateway, and SD-WAN WANOP appliance authorization bypass ·
Other Citrix flaws
- CVE-2026-88779, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88772, Citrix NetScaler: improper restriction of operations within the bounds of a memory buffer ·
- CVE-2026-88771, Citrix NetScaler: improper input validation ·
- CVE-2026-19490, Citrix NetScaler: authentication bypass using an alternate path or channel ·
- CVE-2026-8452, Citrix NetScaler ADC and NetScaler Gateway: improper restriction of operations within the bounds of a memory buffer ·
Other path traversal flaws
- CVE-2025-61624, Fortinet products: path traversal ·
- CVE-2021-3199, ONLYOFFICE Docs: server path traversal ·
- CVE-2026-104286, Fortinet FortiMail: path traversal ·
- CVE-2026-93616, Check Point products: path traversal ·
- CVE-2026-66384, JFrog Artifactory: improper limitation of a pathname to a restricted directory ·
Added the same day
- CVE-2021-42258, BQE BillQuick Web Suite: SQL injection ·
- CVE-2021-42013, Apache HTTP Server: path traversal ·
- CVE-2021-41773, Apache HTTP Server: path traversal ·
- CVE-2021-40539, Zoho ManageEngine: aDSelfService plus authentication bypass ·
- CVE-2021-40444, Microsoft MSHTML: remote code execution ·
Every Citrix flaw on CISA’s list · Everything added in November 2021
References
- ^ Cybersecurity and Infrastructure Security Agency. “Citrix ADC, Gateway, and SD-WAN WANOP Appliance Code Execution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 3 Nov 2021.
- ^ National Institute of Standards and Technology. “CVE-2019-19781 Detail”. National Vulnerability Database, published 27 Dec 2019.
- ^ Citrix. Advisories and fixes: support.citrix.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 1.000, percentile 100.0, 31 Oct 2026.
- CVE Program. “CVE-2019-19781”. 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.