{"id":"CVE-2021-28799","aliases":["EUVD-2021-15455","GHSA-4v9x-j7pr-8wxq"],"status":"published","title":"Improper Authorization Vulnerability in HBS 3 (Hybrid Backup Sync)","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 .","severity":{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.7825,"percentile":0.99582,"model":"v2026.06.15"},"facts":{"in_kev":true,"known_exploited":true,"public_exploit":false,"fix_available":false},"cwes":["CWE-285","CWE-863"],"published":"2021-05-13T02:55:13Z","modified":"2026-06-17T03:46:53Z","kev":{"date_added":"2022-03-31","due_date":"2022-04-21","required_action":"Apply updates per vendor instructions.","known_ransomware_use":"Known"},"exploitation":[{"source":"euvd","since":"2022-03-31"},{"source":"kev","since":"2022-03-31"}],"exploits":[{"source":"nuclei","id":"CVE-2021-28799","title":"QNAP HBS 3 - Broken Access Control","type":"detection template","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-28799.yaml"}],"products":[{"vendor":"qnap","product":"hybrid_backup_sync"},{"vendor":"qnap","product":"network attached storage (nas)"},{"vendor":"qnap systems inc.","product":"hbs 1.3"},{"vendor":"qnap systems inc.","product":"hbs 2"},{"vendor":"qnap systems inc.","product":"hbs 3"}],"references":[{"url":"https://www.qnap.com/en/security-advisory/QSA-21-13","tags":["x_refsource_MISC","x_transferred","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28799","tags":["government-resource","US Government Resource"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-28799"},{"url":"https://github.com/advisories/GHSA-4v9x-j7pr-8wxq"}],"sources":{"cve":[{"id":"CVE-2021-28799","title":"Improper Authorization Vulnerability in HBS 3 (Hybrid Backup Sync)","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 .","status":"published","published":"2021-05-13T02:55:13.827Z","modified":"2025-10-21T23:25:45.551Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"cna"}],"cwes":["CWE-285"],"updated_at":"2026-11-02T14:33:08.811269Z"}],"euvd":[{"id":"EUVD-2021-15455","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 .","status":"published","published":"2021-05-13T02:55:13Z","modified":"2025-10-21T23:25:45Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"exploited_since":"2022-03-31","updated_at":"2026-11-02T20:31:25.308373Z"}],"ghsa":[{"id":"GHSA-4v9x-j7pr-8wxq","title":"An improper authorization vulnerability has been reported to affect QNAP NAS running HBS 3 ...","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 .","status":"published","published":"2022-05-24T19:02:24Z","modified":"2025-10-22T00:32:13Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-285","CWE-863"],"updated_at":"2026-11-02T15:04:04.786232Z"}],"kev":[{"id":"CVE-2021-28799","title":"QNAP NAS Improper Authorization Vulnerability","description":"QNAP NAS running HBS 3 contains an improper authorization vulnerability which can allow remote attackers to log in to a device.","cwes":["CWE-285"],"kev":{"date_added":"2022-03-31","due_date":"2022-04-21","required_action":"Apply updates per vendor instructions.","known_ransomware_use":"Known"},"updated_at":"2026-11-02T17:00:16.541131Z"}],"nvd":[{"id":"CVE-2021-28799","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 .","status":"published","published":"2021-05-13T03:15:06.843Z","modified":"2026-06-17T03:46:53.003Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical","assessor":"secondary"},{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary"},{"version":"2.0","score":7.5,"vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","level":"high","assessor":"primary"}],"cwes":["CWE-285"],"updated_at":"2026-11-02T14:06:53.343329Z"}]}}