{"cve":{"cve_id":"CVE-2021-28799","is_kev":true,"kev_date_added":"2022-03-31","kev_vendor_project":"QNAP","kev_product":"Network Attached Storage (NAS)","kev_vulnerability_name":"QNAP NAS Improper Authorization Vulnerability","kev_short_description":"QNAP NAS running HBS 3 contains an improper authorization vulnerability which can allow remote attackers to log in to a device.","kev_required_action":"Apply updates per vendor instructions.","kev_due_date":"2022-04-21","kev_known_ransomware":true,"kev_notes":"https://nvd.nist.gov/vuln/detail/CVE-2021-28799","kev_cwes":["CWE-285"],"epss_score":0.78395,"epss_percentile":0.99525,"epss_as_of":"2026-06-23","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 .","published_at":"2021-05-13T02:55:13.827000Z","last_modified_at":null,"cvss_v3_score":10.0,"cvss_v3_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","cvss_v3_severity":"CRITICAL","cvss_v4_score":null,"cvss_v4_vector":null,"cvss_v4_severity":null,"ssvc_decision":null,"ssvc_exploitation":"active","ssvc_automatable":true,"ssvc_technical_impact":"total","cwes":["CWE-285"],"nvd_references":["https://www.qnap.com/en/security-advisory/QSA-21-13"],"vuln_status":null,"trending_score":null,"is_trending":false,"has_trended":false,"trended_number_one":false,"trending_peak_score":null,"trending_peak_rank":null,"started_trending_at":null,"trended_number_one_at":null,"summary_generated":null,"summary_generated_at":null,"summary_model":null,"created_at":"2026-06-24T00:09:31.350578Z","updated_at":"2026-06-28T23:15:26.101164Z"},"effective_severity":"CRITICAL","badges":["kev","ransomware","poc","epss"],"impact_analysis":[],"cvss_v3_decoded":{"version":"3.1","metrics":[{"metric":"AV","name":"Attack Vector","value":"N","value_label":"Network"},{"metric":"AC","name":"Attack Complexity","value":"L","value_label":"Low"},{"metric":"PR","name":"Privileges Required","value":"N","value_label":"None"},{"metric":"UI","name":"User Interaction","value":"N","value_label":"None"},{"metric":"S","name":"Scope","value":"C","value_label":"Changed"},{"metric":"C","name":"Confidentiality","value":"H","value_label":"High"},{"metric":"I","name":"Integrity","value":"H","value_label":"High"},{"metric":"A","name":"Availability","value":"H","value_label":"High"}]},"cvss_v4_decoded":{"version":null,"metrics":[]},"affected":[{"vendor_slug":"qnap-systems-inc.","vendor_name":"QNAP Systems Inc.","product_slug":"hbs-1.3","product_name":"HBS 1.3","version_start":"all versions","version_start_inclusive":true,"version_end":"all versions","version_end_inclusive":true,"cpe23_uri":"cve5:qnap-systems-inc.:hbs-1.3:all versions:all versions"},{"vendor_slug":"qnap-systems-inc.","vendor_name":"QNAP Systems Inc.","product_slug":"hbs-2","product_name":"HBS 2","version_start":"all versions","version_start_inclusive":true,"version_end":"all versions","version_end_inclusive":true,"cpe23_uri":"cve5:qnap-systems-inc.:hbs-2:all versions:all versions"},{"vendor_slug":"qnap-systems-inc.","vendor_name":"QNAP Systems Inc.","product_slug":"hbs-3","product_name":"HBS 3","version_start":"unspecified","version_start_inclusive":true,"version_end":"v16.0.0415","version_end_inclusive":false,"cpe23_uri":"cve5:qnap-systems-inc.:hbs-3:unspecified:v16.0.0415"},{"vendor_slug":"qnap-systems-inc.","vendor_name":"QNAP Systems Inc.","product_slug":"hbs-3","product_name":"HBS 3","version_start":"unspecified","version_start_inclusive":true,"version_end":"v3.0.210412","version_end_inclusive":false,"cpe23_uri":"cve5:qnap-systems-inc.:hbs-3:unspecified:v3.0.210412"},{"vendor_slug":"qnap-systems-inc.","vendor_name":"QNAP Systems Inc.","product_slug":"hbs-3","product_name":"HBS 3","version_start":"unspecified","version_start_inclusive":true,"version_end":"v3.0.210411","version_end_inclusive":false,"cpe23_uri":"cve5:qnap-systems-inc.:hbs-3:unspecified:v3.0.210411"},{"vendor_slug":"qnap-systems-inc.","vendor_name":"QNAP Systems Inc.","product_slug":"hbs-3","product_name":"HBS 3","version_start":"unspecified","version_start_inclusive":true,"version_end":"v16.0.0419","version_end_inclusive":false,"cpe23_uri":"cve5:qnap-systems-inc.:hbs-3:unspecified:v16.0.0419"}],"exploit_refs":[{"source":"nuclei","kind":"nuclei","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-28799.yaml","title":"QNAP HBS 3 - Broken Access Control","author":"daffainfo","disclosed_at":null}],"news":[],"references":[{"url":"https://www.qnap.com/en/security-advisory/QSA-21-13","source_type":"MISC","tags":[]}],"timeline":[{"type":"published","at":"2021-05-13T02:55:13.827000Z","label":"CVE published","source":null},{"type":"cisa_reported","at":"2022-03-31T00:00:00Z","label":"Added to CISA KEV catalog","source":"kev"},{"type":"poc_available","at":"2026-06-24T00:29:48.638073Z","label":"Public PoC available","source":"nuclei"},{"type":"ssvc_changed","at":"2026-06-24T00:31:40.594775Z","label":"SSVC decision revised","source":"vulnrichment"},{"type":"ssvc_changed","at":"2026-06-24T00:31:40.594775Z","label":"SSVC decision revised","source":"vulnrichment"},{"type":"ssvc_changed","at":"2026-06-24T00:31:40.594775Z","label":"SSVC decision revised","source":"vulnrichment"},{"type":"cvss_changed","at":"2026-06-24T00:31:40.594775Z","label":"CVSS score revised","source":"vulnrichment"},{"type":"cvss_changed","at":"2026-06-24T00:31:40.594775Z","label":"CVSS score revised","source":"vulnrichment"},{"type":"cvss_changed","at":"2026-06-24T00:31:40.594775Z","label":"CVSS score revised","source":"vulnrichment"}]}