CVE-2021-28799
Improper Authorization Vulnerability in HBS 3 (Hybrid Backup Sync)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
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 .
Official description from the CVE record, published by qnap. Copyright © 1999-2026 The MITRE Corporation. See /security/cve/legal for the CVE license. View the record on cve.org
Key data
CVSS 3.1 Critical 10.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack vector: Network
The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity: Low
No special conditions are needed. The attack can be repeated at will.
Privileges required: None
No account or privileges are needed.
User interaction: None
No action from any user is needed.
Scope: Changed
The impact can reach other components beyond the vulnerable one.
Confidentiality impact: High
Serious or total effect on the secrecy of data.
Integrity impact: High
Serious or total effect on the trustworthiness of data.
Availability impact: High
Serious or total effect on availability.
| Metric | Value | What it means |
|---|---|---|
| Attack vector | Network | The vulnerable component can be reached over a network, possibly from the Internet. |
| Attack complexity | Low | No special conditions are needed. The attack can be repeated at will. |
| Privileges required | None | No account or privileges are needed. |
| User interaction | None | No action from any user is needed. |
| Scope | Changed | The impact can reach other components beyond the vulnerable one. |
| Confidentiality impact | High | Serious or total effect on the secrecy of data. |
| Integrity impact | High | Serious or total effect on the trustworthiness of data. |
| Availability impact | High | Serious or total effect on availability. |
CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at first.org/cvss.
EPSS
- Score
- 0.78250 (78.3% probability)
- Percentile
- 99.6%
- Scores of
- Nov 10, 2026
- Model
- v2026.06.15
CISA Known Exploited Vulnerabilities
- Name in the catalog
- QNAP NAS Improper Authorization Vulnerability
- Added to the catalog
- Mar 31, 2022
- Federal due date
- Apr 21, 2022
- Ransomware campaigns
- Known use
CISA assessment as of Feb 4, 2025
- Exploitation
- Recorded by CISA as active
- Automatable
- yes
- Technical impact
- total
Weakness (CWE)
- CWE-285Improper Authorization
Affected products
QNAP Systems Inc. HBS 3
- affected: unspecified up to before v16.0.0415
QNAP Systems Inc. HBS 3
- affected: unspecified up to before v3.0.210412
QNAP Systems Inc. HBS 3
- affected: unspecified up to before v3.0.210411
QNAP Systems Inc. HBS 3
- affected: unspecified up to before v3.0.210411
QNAP Systems Inc. HBS 3
- affected: unspecified up to before v16.0.0419
QNAP Systems Inc. HBS 3
- affected: unspecified up to before v16.0.0419
QNAP Systems Inc. HBS 2
- unaffected: all versions
QNAP Systems Inc. HBS 1.3
- unaffected: all versions
References
Timeline
- ID reserved
- Record published
- Added to CISA KEV
- Record last updated
Look up another CVE
About CubePath
Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:29 UTC. Sources and licenses