CVE DATABASE / CVE-2021-28799

CVE-2021-28799

QNAP NAS Improper Authorization Vulnerability

CVSS 10 · CRITICAL ⚠ CISA KEV — ACTIVELY EXPLOITED RANSOMWARE

On the CISA KEV catalog

Confirmed exploited in the wild. Added 2022-03-31. Federal remediation due 2022-04-21.
Required action: Apply updates per vendor instructions.

Summary

An improper authorization vulnerability has been reported to affect QNAP NAS running HBS 3 (Hybrid Backup Sync. ) If exploited, the vulnerability allows remote attackers to log in to a device. This issue affects: QNAP Systems Inc. HBS 3 versions prior to v16.0.0415 on QTS 4.5.2; versions prior to v3.0.210412 on QTS 4.3.6; versions prior to v3.0.210411 on QTS 4.3.4; versions prior to v3.0.210411 on QTS 4.3.3; versions prior to v16.0.0419 on QuTS hero h4.5.1; versions prior to v16.0.0419 on QuTScloud c4.5.1~c4.5.4. This issue does not affect: QNAP Systems Inc. HBS 2 . QNAP Systems Inc. HBS 1.3 .

CVSS 3.1 breakdown

Base score	10 (CRITICAL)
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack vector	NETWORK
Attack complexity	LOW
Privileges required	NONE
User interaction	NONE
Scope	CHANGED
Confidentiality	HIGH
Integrity	HIGH
Availability	HIGH

Weakness type (CWE)

CWE-285

Affected products

Qnap hybrid backup syncQnap qtsQnap quts heroQnap qutscloud

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References

Data: NIST NVD + CISA KEV. NVD last modified 2025-11-03. Always verify against the vendor advisory before acting.