Exploitation evidence
Known exploited · CISA KEV listed
Added 2022-03-31. Ransomware campaign use: Known.
CISA required action: Apply updates per vendor instructions.
CISA due date: 2022-04-21. This is the catalog’s deadline, not an assessment of your organization’s exposure.
KEV checked 13 Nov 2026, 00:20 Jerusalem · Original catalog ↗Reported products and versions
QNAP Systems Inc. / HBS 3
Default status: Not specified
- affected: unspecified to < v16.0.0415 (custom)
QNAP Systems Inc. / HBS 3
Default status: Not specified
- affected: unspecified to < v3.0.210412 (custom)
QNAP Systems Inc. / HBS 3
Default status: Not specified
- affected: unspecified to < v3.0.210411 (custom)
QNAP Systems Inc. / HBS 3
Default status: Not specified
- affected: unspecified to < v3.0.210411 (custom)
QNAP Systems Inc. / HBS 3
Default status: Not specified
- affected: unspecified to < v16.0.0419 (custom)
QNAP Systems Inc. / HBS 3
Default status: Not specified
- affected: unspecified to < v16.0.0419 (custom)
QNAP Systems Inc. / HBS 2
Default status: Not specified
- unaffected: all versions
QNAP Systems Inc. / HBS 1.3
Default status: Not specified
- unaffected: all versions
Fixes and workarounds
QNAP have already fixed this vulnerability in the following versions of HBS 3: QTS 4.5.2: HBS 3 v16.0.0415 and later QTS 4.3.6: HBS 3 v3.0.210412 and later QTS 4.3.3 and 4.3.4: HBS 3 v3.0.210411 and later QuTS hero h4.5.1: HBS 3 v16.0.0419 and later QuTScloud c4.5.1~c4.5.4: HBS 3 v16.0.0419 and later
Sources and related reporting
Observed change timeline
History begins when Egret first downloads each source. It is not the complete upstream CVE history.
12 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-12",
"epss": 0.7825,
"percentile": 0.99585
}10 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-10",
"epss": 0.7825,
"percentile": 0.99582
}09 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-09",
"epss": 0.7825,
"percentile": 0.99582
}08 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-08",
"epss": 0.7825,
"percentile": 0.99582
}07 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-07",
"epss": 0.7825,
"percentile": 0.99581
}06 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-06",
"epss": 0.7825,
"percentile": 0.99581
}06 Nov 2026, 06:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-05",
"epss": 0.7825,
"percentile": 0.9958
}05 Nov 2026, 18:20 Jerusalem · CVE Program record changed
Stored CNA snapshot at this observation.
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}04 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-04",
"epss": 0.7825,
"percentile": 0.99579
}03 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-03",
"epss": 0.7825,
"percentile": 0.99579
}03 Nov 2026, 02:22 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-02",
"epss": 0.7825,
"percentile": 0.99579
}03 Nov 2026, 02:22 Jerusalem · CISA KEV status changed
Stored KEV snapshot at this observation.
{
"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"
}