Exploited. On CISA's list since 2022-05-24, and used by ransomware.

QNAP NAS File Station Cross-Site Scripting Vulnerability

CVE-2018-19943 · QNAP Network Attached Storage (NAS) · Published 2020-10-28

How bad would it be?

5.4 out of 10

CVSS rates it medium.

How likely is it to be used?

23%

Estimated chance of exploitation in the next 30 days, higher than 97% of all scored flaws (EPSS, 2026-10-29).

Is it already being used?

Yes

CISA has seen it exploited in real attacks. For US government agencies the fix is deadline passed 1599 days ago (2022-06-14).

What CISA says to do

Apply updates per vendor instructions.

A cross-site scripting vulnerability affecting QNAP NAS File Station could allow remote attackers to inject malicious code.

nvd.nist.gov

What the flaw is

If exploited, this cross-site scripting vulnerability could allow remote attackers to inject malicious code. QNAP has already fixed these issues in the following QTS versions. QTS 4.4.2.1270 build 20200410 and later QTS 4.4.1.1261 build 20200330 and later QTS 4.3.6.1263 build 20200330 and later QTS 4.3.4.1282 build 20200408 and later QTS 4.3.3.1252 build 20200409 and later QTS 4.2.6 build 20200421 and later

From the NVD.

Fixes and advisories

www.qnap.comVendor Advisory
www.qnap.comVendor Advisory

Learn this

Explore this week’s weaknesses and all learning topics

Understand the kind of weakness behind this flaw. These resources teach the weakness, rather than reproduce this specific CVE. Follow the vendor's advice above to fix the affected product.

Cross-site scripting

Untrusted content becomes code running in another visitor's browser.

CWE-79 · CISA KEV; NVD record: nvd@nist.gov; NVD record: security@qnapsecurity.com.tw

Reading and practice labs · Free account for labs. Basic HTTP knowledge; some labs use Burp Suite.

Explore the labs at PortSwigger Web Security Academy How it is prevented

CWE-80 · CISA KEV; NVD record: security@qnapsecurity.com.tw. We have not selected a close learning match for this label.

CWE is a catalogue of weakness types. Labels come from the sources shown and can differ or change. Resource matches reviewed 16 October 2026.

On SentryFeed

No story in the last 14 days has mentioned it.

Exploited flaws from CISA's KEV catalogue. Chance of exploitation from EPSS by FIRST. Descriptions and scores from the NVD. This product uses the NVD API but is not endorsed or certified by the NVD.