CISA KEV Medium Cross-site scripting

CVE-2018-19953 — QNAP NAS File Station Cross-Site Scripting Vulnerability

If exploited, this cross-site scripting vulnerability could allow remote attackers to inject malicious code. QNAP has already fixed the issue in the following QTS versions. QTS 4.4.2.1231 on build 20200302; QTS 4.4.1.1201 on build 20200130; QTS 4.3.6.1218 on build 20200214; QTS 4.3.4.1190 on build 20200107; QTS 4.3.3.1161 on build 20200109; QTS 4.2.6 on build 20200109.

Published Oct 28, 2020 · Updated Oct 13, 2026 · Sources: CISA Known Exploited Vulnerabilities, CVE Program (cve.org) e CISA ADP, NIST National Vulnerability Database, GitHub Security Advisories · CNA: qnap

High

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

CISA KEV · May 24, 2022 R used by ransomware (CISA)

How the score was calculated

Confirmed exploitation (CISA KEV)+35
Used in ransomware campaigns (CISA)+10
EPSS 29% (30-day exploitation probability)+15
Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Confirmed

CISA KEV, listed May 24, 2022

EPSS FIRST

28.98%

ahead of 98% of scored CVEs · Oct 14, 2026

Affects

Qnap

Qts and 1 more

CVSS base

6.1

Medium · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Active

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

CISA required action CISA

Apply updates per vendor instructions.

US federal deadline: Jun 14, 2022 — passed 1584 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Qnap Qts, QNAP Systems Inc. QTS).
Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Exploitation requires user interaction: tighten email/web filtering and warn affected users.
EPSS ahead of 98% of scored CVEs: prioritize it in the patch queue.
Search available logs for exploit probes matching the vulnerability class (cross-site scripting), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Qnap	Qts	≥ 4.3.6 and < 4.3.6.1218version 4.2.6-build_20191107version 4.2.6-build_20190921version 4.2.6-build_20190730version 4.2.6-build_20190322version 4.2.6-build_20170517version 4.2.6≥ 4.4.2 and < 4.4.2.1231 and 4 more ≥ 4.4.0 and < 4.4.1.1201≥ 4.3.4 and < 4.3.4.1190≥ 4.3.1.0013 and < 4.3.3.1161< 4.2.6	Vulnerable	NIST National Vulnerability Database
QNAP Systems Inc.	QTS	< 4.4.2.1231< 4.2.6< 4.3.3.1161< 4.3.4.1190< 4.3.6.1218< 4.4.1.1201	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
6.1	CVSS 3.1	Medium	2.8	2.7	nvd@nist.gov via NIST National Vulnerability Database
6.1	CVSS 3.1	Medium	2.8	2.7	134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
6.1	CVSS 3.1	Medium	—	—	GitHub, Inc. via GitHub Security Advisories
6.1	CVSS 3.1	Medium	—	—	CISA-ADP via CVE Program (cve.org) e CISA ADP
4.3	CVSS 2.0	Medium	8.6	2.9	nvd@nist.gov via NIST National Vulnerability Database

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-79 · Cross-site Scripting (XSS)

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

Listed

May 24, 2022

Federal deadline

Jun 14, 2022

passed 1584 day(s) ago

Ransomware use

Known

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 28.98%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Monitor CSP violation reports and script payloads in reflected parameters.
Hunt retroactively in logs from before May 24, 2022 (KEV listing): exploitation may have started earlier.

web/proxy/WAF logsnetwork IDS/IPSapplication logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · qnap/qts
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · Published → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record published
Oct 13, 2026
Affected products added · qnap systems inc./qts
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
CVSS changed · 6.1
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Published
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Added to CISA KEV (detected)
Oct 13, 2026 · CISA Known Exploited Vulnerabilities
Record created in this database
Oct 13, 2026 · CISA Known Exploited Vulnerabilities
2022
Added to CISA KEV catalog
May 23, 2022 · CISA
2020
CVE published
Oct 28, 2020 · qnap

Source activity

Repeated readings are counted rather than listed.

3× References added · Oct 13, 2026 – Oct 13, 2026
1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

4 on the record

www.qnap.com/zh-tw/security-advisory/qsa-20-01
x_refsource_MISC, Vendor Advisory, CVE Program (cve.org) e CISA ADP
www.cisa.gov/known-exploited-vulnerabilities-catalog
US Government Resource, NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2018-19953
GitHub Security Advisories
github.com/advisories/GHSA-8h8x-7j55-4jp9
GitHub Security Advisories

Elsewhere on this site

Qnap
every CVE for this vendor

2022-05
what else CISA listed that month

Cross-site scripting
same class

CWE-79
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-24719 QTS, QuTS hero Jun 10, 2026
Medium CVE-2026-24717 QTS, QuTS hero Jun 10, 2026
High CVE-2026-24716 QTS, QuTS hero Jun 10, 2026
High CVE-2025-66281 QTS, QuTS hero Jun 10, 2026
High CVE-2026-22893 QTS, QuTS hero Jun 10, 2026
High CVE-2025-66280 QTS, QuTS hero Jun 10, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2018-19953 is "QNAP NAS File Station Cross-Site Scripting Vulnerability", rated Medium. It affects Qts (Qnap); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 6.1 describes technical severity. EPSS 28.98% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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