CVE-2021-28806: DOM-Based XSS Vulnerability in QTS and QuTS hero

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-06-03 · updated 2026-06-17
Weakness: CWE-79

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.

Affected products

QNAP QTS: before 4.5.3.1652 — fixed in 4.5.3.1652
QNAP Systems Inc. QuTS hero: before h4.5.2.1638 — fixed in h4.5.2.1638
QNAP Systems Inc. QuTScloud: before c4.5.5.1656 — fixed in c4.5.5.1656

How to fix

Upgrade to a fixed version: QNAP QTS 4.5.3.1652; QNAP Systems Inc. QuTS hero h4.5.2.1638; QNAP Systems Inc. QuTScloud c4.5.5.1656. Check the vendor advisory for mitigations.

References

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