CVE-2021-28799

10.0 CRITICAL CISA KEV - Actively Exploited
Published: May 13, 2021 Modified: November 03, 2025

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 .

AI Explanation

Get an AI-powered plain-language explanation of this vulnerability and remediation steps.

Login to generate AI explanation

CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://www.qnap.com/en/security-advisory/QSA-21-13
Source: security@qnapsecurity.com.tw
Vendor Advisory
https://www.qnap.com/en/security-advisory/QSA-21-13
Source: af854a3a-2127-422b-91ae-364da2661108
Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28799
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
US Government Resource

3 reference(s) from NVD

Quick Stats

CVSS v3 Score
10.0 / 10.0
EPSS (Exploit Probability)
80.2%
99th percentile
Exploitation Status
Actively Exploited
Remediation due: 2022-04-21

Weaknesses (CWE)

Affected Vendors

qnap