CVE-2018-19943
CVE-2018-19943 is a security flaw in QNAP Network Attached Storage (NAS), a network drive for storing files and backups at home or in a small office. Attackers can run code in the browser of someone using QNAP Network Attached Storage (NAS) and act as them. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 24 May 2022, and says ransomware gangs have used it.[1]
QNAP Network Attached Storage (NAS) is in things households have: network drives for files and backups, so the fix matters at home as much as at work. Fixed in version 4.4.2.1270, 4.4.1.1261, 4.3.6.1263 and 4.3.4.1282 and others of QTS.
Description
CISA calls it an NAS file station cross-site scripting in QNAP Network Attached Storage (NAS). In its words: “A cross-site scripting vulnerability affecting QNAP NAS File Station could allow remote attackers to inject malicious code.”[1]
The CVE record adds: “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”[2]
The underlying weakness is cross-site scripting (CWE-79), CWE-80, in MITRE’s list of common software weaknesses.
It scores 5.4 out of 10 on the Common Vulnerability Scoring System, which rates it medium, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| QTS | 4.4.2.1270 |
| QTS | 4.4.1.1261 |
| QTS | 4.3.6.1263 |
| QTS | 4.3.4.1282 |
| QTS | 4.3.3.1252 |
| QTS | 4.2.6 |
Every device with QNAP Network Attached Storage (NAS) needs the update.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 24 May 2022, 573 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 14 Jun 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 23%. That’s in the top 3% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
QNAP has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Update QNAP Network Attached Storage (NAS) now.Install the latest update from QNAP on every device that has it, and restart when asked. Then turn on automatic updates, so the next fix arrives on its own.
- Check you’re on 4.4.2.1270 or later.Fixed in version 4.4.2.1270, 4.4.1.1261, 4.3.6.1263 and 4.3.4.1282 and others of QTS. Anything older is what attackers are going after.
- If the maker has stopped updating it, replace it.Network drives stop getting fixes after a few years, and attackers keep a list of the ones that did. If there’s no newer firmware, it won’t be fixed.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 5.4.[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 23%.[4] |
See also
Other QNAP Network Attached Storage (NAS) flaws
- CVE-2018-19953: NAS file station cross-site scripting ·
- CVE-2018-19949: NAS file station command injection ·
- CVE-2021-28799: NAS improper authorization ·
Other QNAP flaws
- CVE-2023-47565, QNAP VioStor NVR: OS command injection ·
- CVE-2022-27593, QNAP Photo Station: externally controlled reference ·
- CVE-2019-7195, QNAP Photo Station: path traversal ·
- CVE-2019-7194, QNAP Photo Station: path traversal ·
- CVE-2019-7193, QNAP QTS: improper input validation ·
Other cross-site scripting flaws
- CVE-2026-42897, Microsoft: exchange server cross-site scripting ·
- CVE-2025-48700, Synacor Zimbra Collaboration Suite (ZCS): cross-site scripting ·
- CVE-2025-66376, Synacor Zimbra Collaboration Suite (ZCS): cross-site scripting ·
- CVE-2025-68461, Roundcube Webmail: cross-site scripting ·
- CVE-2021-26829, OpenPLC ScadaBR: cross-site scripting ·
Added the same day
- CVE-2018-8611, Microsoft Windows: kernel privilege escalation ·
- CVE-2018-19953, QNAP Network Attached Storage (NAS): NAS file station cross-site scripting ·
- CVE-2018-19949, QNAP Network Attached Storage (NAS): NAS file station command injection ·
- CVE-2017-8543, Microsoft Windows: search remote code execution ·
- CVE-2017-8291, Artifex Ghostscript: type confusion ·
Every QNAP flaw on CISA’s list · Everything added in May 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “QNAP NAS File Station Cross-Site Scripting Vulnerability”. Known Exploited Vulnerabilities Catalog, added 24 May 2022.
- ^ National Institute of Standards and Technology. “CVE-2018-19943 Detail”. National Vulnerability Database, published 28 Oct 2020.
- ^ QNAP. Advisories and fixes: qnap.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.227, percentile 97.7, 31 Oct 2026.
- CVE Program. “CVE-2018-19943”. 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.