CVE-2021-28799

highpriority · act · 90OT risk · criticalKEV · exploitedEPSS 0.782 · 100 %ileEURUUS

grimoire priorityP0 · Act now

Exploitable?

Yes · in the wild

CISA KEV

Likely / severe?

78.3% (100th) EPSS

CVSS 7.5 · high

Is it mine?

12 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · fstec_bdu · nvd

added 2022-03-31remediate by 2022-04-21

required action Apply updates per vendor instructions.

EPSS · scored 2026-10-27

QNAP NAS Improper Authorization Vulnerability

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

Technical severity, 0–10. One row per scoring source.

10.0

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · high–critical · 7.5–10

v2.07.5highAV:N/AC:L/Au:N/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 10 · impact 6.4

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 5.9

v3.19.8criticalAV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.110criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:Hsecondary · ENISA EU

v3.110criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:Hsecondary · security@qnapsecurity.com.twexploitability 3.9 · impact 6

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:Hsecondary · CVSS-BT (t0sche)

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: active · Automatable: yes · Technical Impact: totalcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-285USCWE-285USCWE-863US

affected products (12)

Products and version ranges known to be affected.

QNAP Systems Inc. HBS 3unspecified → v16.0.0415enisa_euvdEU
QNAP Systems Inc. HBS 3unspecified → v16.0.0419enisa_euvdEU
QNAP Systems Inc. HBS 3unspecified → v3.0.210411enisa_euvdEU
QNAP Systems Inc. HBS 3unspecified → v3.0.210412enisa_euvdEU
QNAP Systems, Inc. HBS 3 (Hybrid Backup Sync)≤ 3.0.210412fstec_bduRU
QNAP Systems, Inc. HBS 3 (Hybrid Backup Sync)≤ 16.0.0419fstec_bduRU
QNAP Systems, Inc. HBS 3 (Hybrid Backup Sync)≤ 3.0.210411fstec_bduRU
QNAP Systems, Inc. HBS 3 (Hybrid Backup Sync)≤ 16.0.0415fstec_bduRU
qnap hybrid backup sync< 16.0.0415nvdUScpe:2.3:a:qnap:hybrid_backup_sync:*:*:*:*:*:*:*:*
qnap hybrid backup sync< 16.0.0419nvdUScpe:2.3:a:qnap:hybrid_backup_sync:*:*:*:*:*:*:*:*
qnap hybrid backup sync< 3.0.210411nvdUScpe:2.3:a:qnap:hybrid_backup_sync:*:*:*:*:*:*:*:*
qnap hybrid backup sync< 3.0.210412nvdUScpe:2.3:a:qnap:hybrid_backup_sync:*:*:*:*:*:*:*:*

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu nvd NVD CVE.org MITRE

published 2021-05-13modified 2026-06-17

references (6)

External citations — patches, advisories, analysis.

scry

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