Vulnerability Monitor

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CVE-2021-28799


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 .


Security Impact Summary

This vulnerability carries a CRITICAL severity rating with a CVSS v3.1 score of 10.0, indicating it can be exploited remotely over the network with relatively low complexity without requiring user interaction and does not require pre-existing privileges . The vulnerability impacts confidentiality (data exposure), integrity (unauthorized modifications), and availability (service disruption) for affected systems. Impacting 4 products from qnap, from qnap, from qnap and 1 other, organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2021, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.


Published

2021-05-13T03:15:06.843

Last Modified

2025-11-03T15:07:48.747

Status

Analyzed

Source

[email protected]

Severity

CVSSv3.1: 10.0 (CRITICAL)

CVSSv2 Vector

AV:N/AC:L/Au:N/C:P/I:P/A:P

  • Access Vector: NETWORK
  • Access Complexity: LOW
  • Authentication: NONE
  • Confidentiality Impact: PARTIAL
  • Integrity Impact: PARTIAL
  • Availability Impact: PARTIAL
Exploitability Score

10.0

Impact Score

6.4

Weaknesses
  • Type: Secondary
    CWE-285
  • Type: Primary
    NVD-CWE-Other

Affected Vendors & Products
Type Vendor Product Version/Range Vulnerable?
Application qnap hybrid_backup_sync < 16.0.0415 Yes
Operating System qnap qts 4.5.2 No
Application qnap hybrid_backup_sync < 3.0.210412 Yes
Operating System qnap qts 4.3.6 No
Application qnap hybrid_backup_sync < 3.0.210411 Yes
Operating System qnap qts 4.3.3 No
Operating System qnap qts 4.3.4 No
Application qnap hybrid_backup_sync < 16.0.0419 Yes
Operating System qnap quts_hero h4.5.1 No
Application qnap hybrid_backup_sync < 16.0.0419 Yes
Operating System qnap qutscloud ≤ c4.5.4 No

References

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For qnap's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.