DOM-Based XSS Vulnerability in QTS and QuTS hero

published 2021-06-03 5y ago modified 2026-06-17 4mo ago also EUVD-2021-15462

cvss: 5.7; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 43%
public exploits: 0; none known

A DOM-based XSS vulnerability has been reported to affect QNAP NAS running QTS and QuTS hero. If exploited, this vulnerability allows attackers to inject malicious code. This issue affects: QNAP Systems Inc. QTS versions prior to 4.5.3.1652 Build 20210428. QNAP Systems Inc. QuTS hero versions prior to h4.5.2.1638 Build 20210414. QNAP Systems Inc. QuTScloud versions prior to c4.5.5.1656 Build 20210503. This issue does not affect: QNAP Systems Inc. QTS 4.3.6; 4.3.3.

Patch / fix

fixed in 3

QNAP Systems Inc. QTS 4.3.3, 4.3.6, 4.5.3.1652 Build 20210428
QNAP Systems Inc. QuTS hero h4.5.2.1638 Build 20210414
QNAP Systems Inc. QuTScloud c4.5.5.1656 Build 20210503

Is CVE-2021-28806 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Exploit prediction

0.51% chance of exploitation in the next 30 days, higher than 43% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.7	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N
NVD	3.1	5.4	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
NVD	2.0	3.5	AV:N/AC:M/Au:S/C:N/I:P/A:N

Affected products

QNAP Systems Inc. QTS
QNAP Systems Inc. QuTS hero
QNAP Systems Inc. QuTScloud

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

qnap.com /zh-tw/security-advisory/qsa-21-22
vendor-advisory

Sources

CVE List CVE-2021-28806
NVD CVE-2021-28806

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