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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 .","epss":{"date":"2026-11-12","epss":0.7825,"percentile":0.99585},"epss_checked":1794522003,"first_seen":1793665375,"kev":{"cveID":"CVE-2021-28799","cwes":["CWE-285"],"dateAdded":"2022-03-31","dueDate":"2022-04-21","forensicTriage":"No","knownRansomwareCampaignUse":"Known","notes":"https://nvd.nist.gov/vuln/detail/CVE-2021-28799","product":"Network Attached Storage (NAS)","requiredAction":"Apply updates per vendor instructions.","shortDescription":"QNAP NAS running HBS 3 contains an improper authorization vulnerability which can allow remote attackers to log in to a device.","vendorProject":"QNAP","vulnerabilityName":"QNAP NAS Improper Authorization Vulnerability"},"kev_checked":1794522003,"products":"QNAP Systems Inc. HBS 3, QNAP Systems Inc. HBS 2, QNAP Systems Inc. HBS 1.3","references":["https://www.qnap.com/en/security-advisory/QSA-21-13","https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28799"],"score":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":10,"baseSeverity":"CRITICAL","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","provider":"qnap","scope":"CHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","version":"3.1"},"solutions":"QNAP have already fixed this vulnerability in the following versions of HBS 3:\nQTS 4.5.2: HBS 3 v16.0.0415 and later\nQTS 4.3.6: HBS 3 v3.0.210412 and later\nQTS 4.3.3 and 4.3.4: HBS 3 v3.0.210411 and later\nQuTS hero h4.5.1: HBS 3 v16.0.0419 and later\nQuTScloud c4.5.1~c4.5.4: HBS 3 v16.0.0419 and later","state":"PUBLISHED","title":"Improper Authorization Vulnerability in HBS 3 (Hybrid Backup Sync)","updated_at":1794500401,"workarounds":""},"sources":[]}