Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2018-19943

QTS Cross-Site Scripting

QNAP / QTS · affected before 4.4.2.1270

Watch CVE-2018-19943 Browse KEV feed
Severity
CVSS 8.0 · High
Confidence
Confirmed
Exploit status
Exploited in the wild
EPSS
21.5%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2018-19943 is a vulnerability affecting QNAP QTS. If exploited, this cross-site scripting vulnerability could allow remote attackers to inject malicious code. QNAP has already fixed these issues in the following...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is confirmed. Listed in CISA KEV. Also confirmed by third-party sources.

Who is affected?

QNAP / QTS affected before 4.4.2.1270.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

If exploited, this cross-site scripting vulnerability could allow remote attackers to inject malicious code

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

QNAP Systems Inc. Affected
QTS
Before 4.4.2.1270 Before 4.4.1.1261 Before 4.3.6.1263 Before 4.3.4.1282 Before 4.3.3.1252 Before 4.2.6
Published
28 Oct 2020
Exploitation Reported
24 May 2022
Attack vector
Remote
Complexity
High
Privileges
Low
User interaction
Required

Tags

cisa windows malware ransomware

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 24 May 2022

A trusted third party reported exploitation.

Used in malware

CISA

Recorded 24 May 2022

Malware families have been linked to exploitation of this CVE.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

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Source Added
CISA First 2022-05-24 00:00 UTC
CVE 2026-08-13 04:20 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

8.0 High

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H

EPSS

21.5%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE-79 Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) CWE-80

All CVSS Scores

CVSS v3.1 8.0 High

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H

CVSS v2.0 3.5 Low

AV:N/AC:M/Au:S/C:N/I:P/A:N

Timeline

From disclosure to observed exploitation

  1. 04:20 UTC

    KEV confirmed by CVE

    Exploitation attested by an external source

  2. 00:00 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  3. 00:00 UTC

    First public exploitation report

    Exploit observed in malware

  4. 17:55 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 00:00 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2018-19943

Sample API response 
{
  "cve_id": "CVE-2018-19943",
  "confidence": "Confirmed",
  "cvss_score": 8.0,
  "cvss_estimated": false,
  "epss_score": 0.21476,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}