CVE-2021-28799

What the flaw is

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

Description as published by CISA. We have not independently reproduced it.

What CISA requires

Apply updates per vendor instructions.

This deadline is binding on US federal civilian agencies under BOD 22-01. It is not a legal deadline for anyone else, but it is a useful urgency signal — CISA sets it by how actively the flaw is being used, not by CVSS.

Public exploit code

4 public repositories referencing this CVE have been catalogued on GitHub. Treat this as a strong signal to prioritise patching, not as a verified working exploit — many such repositories are scanners, write-ups or forks rather than functional code.

• Ostorlab/KEV
• Ostorlab/known_exploited_vulnerbilities_detectors
• r0eXpeR/supplier
• triw0lf/Security-Matters-22

Vendor advisories

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

Primary sources

• NVD entry — CVSS score, CPE list and references
• CISA KEV catalog — the source for this page
• CVE Record at cve.org