CVE-2021-28799 - CVE House
Back to Database
Status published Critical CVE-2021-28799

Improper Authorization Vulnerability in HBS 3 (Hybrid Backup Sync)

Vulnerability Description

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 .

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

THREAT MONITOR

Am I Vulnerable?

Launch our assessment wizard to check if your infrastructure is exposed to • CVE-2021-28799

Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

  • ZUSO ART

Affected Vendor

QNAP Systems Inc.

View all reports →

Affected Software

HBS 3, HBS 2, HBS 1.3
Vulnerable Versions:
unspecified, all versions

Timeline

Official Publish: May 13th, 2021
Last Modified: October 21st, 2025
Added to House: July 21st, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Weaknesses (CWE)