CVE-2021-28806

Name: CVE-2021-28806
Creator: NVD / NIST
Published: 2021-06-03T03:15:08.437+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.4/10EPSS 0.51%

Last modified Jun 17, 2026

CVE-2021-28806 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. 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. EPSS estimates a 0.51% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

5.4/10

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

EPSS Probability

0.51%

39.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Qnap	Qts	< 4.5.3.1652
Qnap	Quts Hero	< h4.5.2.1638
Qnap	Qutscloud	< c4.5.5.1656

References

https://www.qnap.com/zh-tw/security-advisory/qsa-21-22Vendor Advisory
https://www.qnap.com/zh-tw/security-advisory/qsa-21-22Vendor Advisory

Timeline

Published: Jun 3, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-28806?

How severe is CVE-2021-28806?

CVE-2021-28806 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.51% probability of exploitation in the next 30 days.

How do I fix CVE-2021-28806?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-28806?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST