CVE-2021-28799: QNAP NAS Improper Authorization Vulnerability

CISA Known Exploited Vulnerabilities

Name

QNAP NAS Improper Authorization Vulnerability

Vendor

QNAP

Product

Network Attached Storage (NAS)

Added to the catalog

2022-03-31

Due date for US federal agencies

2022-04-21

Weaknesses

CWE-285

Catalog version

2026.10.30

QNAP NAS running HBS 3 contains an improper authorization vulnerability which can allow remote attackers to log in to a device.

Required action (CISA)

Apply updates per vendor instructions.

Ransomware use: CISA marks this vulnerability as known to be used in ransomware campaigns. CISA does not say which group used it.

Links in CISA's notes

• https://nvd.nist.gov/vuln/detail/CVE-2021-28799

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2021-05-13T03:15:06.843

Last modified

2026-06-17T03:46:53.003

Weaknesses

CWE-285, NVD-CWE-Other

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 .

References

• https://www.qnap.com/en/security-advisory/QSA-21-13 (Vendor Advisory)
• https://www.qnap.com/en/security-advisory/QSA-21-13 (Vendor Advisory)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28799 (US Government Resource)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:41:51.476Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-28799

CVE record

Title (CNA)

Improper Authorization Vulnerability in HBS 3 (Hybrid Backup Sync)

Assigner

qnap

State

PUBLISHED

Published

2021-05-13T02:55:13.827Z

Updated

2025-10-21T23:25:45.551Z

Problem types

CWE-285 Improper Authorization

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 .

References

• https://www.qnap.com/en/security-advisory/QSA-21-13

Read on 2026-11-03T01:07:19.883Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/28xxx/CVE-2021-28799.json

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

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