CVE-2021-28798: Relative Path Traversal Vulnerability in QTS and QuTS hero

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-05-21 · updated 2026-06-17
Weakness: CWE-23

Description

A relative path traversal vulnerability has been reported to affect QNAP NAS running QTS and QuTS hero. If exploited, this vulnerability allows attackers to modify files that impact system integrity. QNAP have already fixed this vulnerability in the following versions: QTS 4.5.2.1630 Build 20210406 and later QTS 4.3.6.1663 Build 20210504 and later QTS 4.3.3.1624 Build 20210416 and later QuTS hero h4.5.2.1638 Build 20210414 and later QNAP NAS running QTS 4.5.3 are not affected.

Affected products

QNAP QTS: from 4.3.2.0144 before 4.3.3.1624; from 4.3.4.0000 before 4.3.6.1663; from 4.4.0000 before 4.5.2.1630 — fixed in 4.3.3.1624, 4.3.6.1663, 4.5.2.1630
QNAP Systems Inc. QuTS hero: before h4.5.2.1638 — fixed in h4.5.2.1638

How to fix

Upgrade to a fixed version: QNAP QTS 4.3.3.1624, 4.3.6.1663, 4.5.2.1630; QNAP Systems Inc. QuTS hero h4.5.2.1638. Check the vendor advisory for mitigations.

References

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