# 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 .

- Page: https://www.vulneraibility.com/cve/CVE-2021-28799
- CVSS: 10.0
- Known exploited: yes, in CISA KEV since 2022-03-31; CISA due date 2022-04-21; known ransomware use
- EPSS: 78.25% (percentile 99.6)
- Detection templates only, no public exploit found: 1 Nuclei template
- CISA SSVC: exploitation active, automatable yes, technical impact total (assessed 2025-02-04)
- Weakness: CWE-285
- Published: 2021-05-13

## Affected versions

- QNAP Systems Inc. HBS 3: affected < v16.0.0415; < v3.0.210412; < v3.0.210411; < v16.0.0419

A version outside these ranges is not a statement that it is unaffected.

## References

- [other] https://www.qnap.com/en/security-advisory/QSA-21-13
- [other] https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28799

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Summary, impact and action are written by the vulneraibility.com AI analysis pipeline from the CVE record, NVD, CISA and FIRST data; verify against the references.