{"schemaVersion":3,"id":"CVE-2021-28799","aliases":[],"status":"published","duplicateOf":null,"title":"QNAP NAS Improper Authorization Vulnerability","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 .","dates":{"published":"2021-05-13T02:55:13.827Z","modified":"2025-10-21T23:25:45.551Z","reserved":null,"kevAdded":["2022-03-31T00:00:00.000Z"],"kevDue":["2022-04-21T00:00:00.000Z"]},"cvss":{"headline":{"score":10,"severity":"critical","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":10,"severity":"critical","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":9.8,"severity":"critical","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","exploitability":null,"impact":null,"computed":false},{"version":"2.0","versionLabel":"v2.0","source":"NVD","score":7.5,"severity":"high","vector":"AV:N/AC:L/Au:N/C:P/I:P/A:P","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.7825,"percentile":0.9958,"severity":"critical","asOf":"2026-10-21T00:00:00.000Z","change":{"pp":0,"baselineDate":"2026-09-21T00:00:00.000Z","baselineScore":0.7825},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.7825,"percentile":0.9958}],"last30":[{"date":"2026-09-21T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.7825,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.7825,"percentile":0.9958}]},"kev":{"state":"listed","entries":[{"source":"cisa","sourceLabel":"CISA","dateAdded":"2022-03-31T00:00:00.000Z","dueDate":"2022-04-21T00:00:00.000Z","requiredAction":"Apply updates per vendor instructions.","name":"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.","notes":[{"type":"url","href":"https://nvd.nist.gov/vuln/detail/CVE-2021-28799","label":"nvd.nist.gov/vuln/detail/CVE-2021-28799"}],"vendor":"QNAP","product":"Network Attached Storage (NAS)","ransomware":true,"ransomwareUse":"Known","exploitationType":null}],"listedCount":1,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":true,"entry":{"source":"cisa","sourceLabel":"CISA","dateAdded":"2022-03-31T00:00:00.000Z","dueDate":"2022-04-21T00:00:00.000Z","requiredAction":"Apply updates per vendor instructions.","name":"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.","notes":[{"type":"url","href":"https://nvd.nist.gov/vuln/detail/CVE-2021-28799","label":"nvd.nist.gov/vuln/detail/CVE-2021-28799"}],"vendor":"QNAP","product":"Network Attached Storage (NAS)","ransomware":true,"ransomwareUse":"Known","exploitationType":null}},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"known","sources":["cisa"]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-285","name":"Improper Authorization","description":"The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.","type":"weakness","status":"Draft","abstraction":"Class","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/285.html"}],"affected":[{"vendor":"qnap systems inc.","product":"hbs 3","name":"HBS 3","label":"hbs 3","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ unspecified, < v16.0.0415","noFixRecorded":false,"fixedIn":null},{"text":"≥ unspecified, < v3.0.210412","noFixRecorded":false,"fixedIn":null},{"text":"≥ unspecified, < v3.0.210411","noFixRecorded":false,"fixedIn":null},{"text":"≥ unspecified, < v16.0.0419","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ unspecified, < v16.0.0415 | ≥ unspecified, < v3.0.210412 | ≥ unspecified, < v3.0.210411 | ≥ unspecified, < v16.0.0419","eol":null,"hubHref":"/vendor/qnap_systems_inc/hbs_3"},{"vendor":"qnap","product":"hybrid_backup_sync","name":"hybrid backup sync","label":"hybrid_backup_sync","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 16.0.0415","noFixRecorded":false,"fixedIn":null},{"text":"< 3.0.210412","noFixRecorded":false,"fixedIn":null},{"text":"< 3.0.210411","noFixRecorded":false,"fixedIn":null},{"text":"< 16.0.0419","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 16.0.0415 | < 3.0.210412 | < 3.0.210411 | < 16.0.0419","eol":null,"hubHref":"/vendor/qnap/hybrid_backup_sync"}],"affectedCount":2,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://www.qnap.com/en/security-advisory/QSA-21-13","label":"www.qnap.com/en/security-advisory/QSA-21-13","hostname":"www.qnap.com","tags":["X Refsource MISC","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28799","label":"www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28799","hostname":"www.cisa.gov","tags":["Government Resource","US Government Resource"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2021-05-13T02:55:13.827Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"kev-added","date":"2022-03-31T00:00:00.000Z","label":"Added to CISA KEV","detail":"QNAP NAS Improper Authorization Vulnerability","source":"cisa"},{"kind":"kev-due","date":"2022-04-21T00:00:00.000Z","label":"CISA remediation due","detail":"Apply updates per vendor instructions.","source":"cisa"},{"kind":"modified","date":"2025-10-21T23:25:45.551Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":90,"level":"critical","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-22T10:26:42.876Z","stale":false,"partial":false}}