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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 14 Jun 2022. Known ransomware use
QtsOperating system · Qnap

CVE-2018-19943

MEDIUM · 5.4 CVSS v3.1 Published 2020-10-28
Fix available
A fix is available. Upgrade to 4.2.6 / 4.3.3.1252 or later.
See remediation →
98/100
Remediation priority · Urgent
In the wild Ransomware Remotely reachable

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This is a cross-site scripting (XSS) vulnerability in QNAP QTS firmware that allows remote attackers to inject malicious JavaScript code into the web interface. When other users access the affected interface, the injected script executes in their browser context, potentially stealing session cookies or performing actions on behalf of authenticated users.

MitigationUpgrade QTS to one of the fixed versions (4.4.2.1270, 4.4.1.1261, 4.3.6.1263, 4.3.4.1282, 4.3.3.1252, or 4.2.6 or later depending on your current branch). If patching is not immediately feasible, restrict administrative interface access to trusted networks only.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
QtsOperating system
Affected:< 4.2.6>= 4.3.1.0013, < 4.3.3.1252>= 4.3.4, < 4.3.4.1282>= 4.3.6, < 4.3.6.1263>= 4.4.0, < 4.4.1.1261>= 4.4.2, < 4.4.2.1270= 4.2.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify QTS firmware version via web interface
    Log into the QNAP admin web console. The version is typically displayed on the login page or accessible via Control Panel > System > General Settings. Note the full version number including build numbers (e.g., 4.3.4.1154).
    Affected if The displayed version falls within any of these ranges: < 4.2.6; >= 4.3.1.0013 and < 4.3.3.1252; >= 4.3.4 and < 4.3.4.1282; >= 4.3.6 and < 4.3.6.1263; >= 4.4.0 and < 4.4.1.1261; >= 4.4.2 and < 4.4.2.1270
  2. Identify QTS firmware version via command line
    Access the NAS via SSH or the built-in Terminal. Run the command 'cat /etc/config/core/version' or 'cat /proc/sys/desc/qts_ver' to retrieve the firmware version number.
    Affected if The version number retrieved matches any of the affected ranges listed above.
  3. Verify web administration interface is accessible
    Confirm that the QTS web interface (typically ports 8080 or 443) is enabled and reachable. Check via Control Panel > System > General Settings > Web Server, or run 'nginx -t' via CLI to verify the web server configuration.
    Affected if The web interface is enabled and the QTS version falls within the affected version ranges, as the XSS payload would be injected into the web interface.

A user is affected if their QNAP QTS firmware version matches any of the vulnerable version ranges AND the web administration interface is accessible.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.2.6 / 4.3.3.1252 / 4.3.4.1282 or later
Fixed in 4.2.64.3.3.12524.3.4.1282
Interim mitigation

Upgrade QTS to one of the fixed versions (4.4.2.1270, 4.4.1.1261, 4.3.6.1263, 4.3.4.1282, 4.3.3.1252, or 4.2.6 or later depending on your current branch). If patching is not immediately feasible, restrict administrative interface access to trusted networks only.

Recommended fix High confidence

QTS 4.2.6 build 20200421+, 4.3.3.1252 build 20200409+, 4.3.4.1282 build 20200408+, 4.3.6.1263 build 20200330+, 4.4.1.1261 build 20200330+, or 4.4.2.1270 build 20200410+ (depending on current branch)

  1. 1. Log into the QNAP NAS administration interface (QTS).
  2. 2. Navigate to Control Panel > System > Firmware Update.
  3. 3. Check the current QTS version and build number under System Information.
  4. 4. Identify which QTS branch you are currently on (4.2.x, 4.3.3.x, 4.3.4.x, 4.3.6.x, or 4.4.x).
  5. 5. Determine the appropriate target version based on your current branch: For QTS 4.2.x, upgrade to 4.2.6 build 20200421 or later; For QTS 4.3.3.x, upgrade to 4.3.3.1252 build 20200409 or later; For QTS 4.3.4.x, upgrade to 4.3.4.1282 build 20200408 or later; For QTS 4.3.6.x, upgrade to 4.3.6.1263 build 20200330 or later; For QTS 4.4.x, upgrade to 4.4.1.1261 build 20200330 or later, or 4.4.2.1270 b
  6. 6. Use the Firmware Update function to install the appropriate version, or download the firmware manually from the QNAP download center and manually update.
  7. 7. After upgrade, verify the new build number matches or exceeds the required build for this security fix.
Caveat Standard firmware update risks apply - ensure backups of critical data and review QNAP release notes for any known issues before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Qts Exploited in the wild — priority engagement
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2018-19943 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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