{"cve_id":"CVE-2021-28799","published":"2021-05-13T03:15:06.843000+00:00","last_modified":"2026-06-17T03:46:53.003000+00:00","vuln_status":"Analyzed","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 .","cvss_version":"3.1","cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","base_score":9.8,"base_severity":"CRITICAL","attack_vector":"NETWORK","privileges_req":"NONE","user_interaction":"NONE","scope":"UNCHANGED","impact_c":"HIGH","impact_i":"HIGH","impact_a":"HIGH","cwe_ids":["CWE-285"],"in_kev":true,"kev_date_added":"2022-03-31","kev_ransomware":true,"epss_score":0.7825,"epss_percentile":0.99579,"cap_rule_version":"0.1.1","stage":"INITIAL_ACCESS","req_access":"NONE","req_vector":"NETWORK","req_user_interaction":false,"grant_access":"USER","caps":["CODE_EXEC"],"terminal":false,"cap_confidence":"high","ingested_at":"2026-09-18T09:41:33.892865+00:00","first_seen":"2021-05-13T03:15:06.843000+00:00","kev_first_seen":"2022-03-31T00:00:00+00:00","novelty_score":0.0,"novelty_reasons":[],"novelty_at":null,"vendors":["qnap"],"products":["hybrid_backup_sync","qts","quts_hero","qutscloud"],"affected":[{"vendor":"qnap","product":"hybrid_backup_sync","ranges":["< 3.0.210411","< 16.0.0415","< 3.0.210412","< 16.0.0419"]}]}