Is CVE-2021-28809 in the CISA KEV catalog?

No. CVE-2021-28809 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-28809?

CVE-2021-28809 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2021-28809?

CVE-2021-28809 has an EPSS score of 15.80% (97th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-28809?

Upgrade hybrid backup sync to 3.0.210506 or later.

CVE & CISA-KEV Catalog

CVE-2021-28809

CRITICALEPSS 97th pctl

9.8

CVSS v3

NVD

Description

An improper access control vulnerability has been reported to affect certain legacy versions of HBS 3. If exploited, this vulnerability allows attackers to compromise the security of the operating system.QNAP have already fixed this vulnerability in the following versions of HBS 3: QTS 4.3.6: HBS 3 v3.0.210507 and later QTS 4.3.4: HBS 3 v3.0.210506 and later QTS 4.3.3: HBS 3 v3.0.210506 and later

CWE-284Improper Access Control CWE-306Missing Authentication for Critical Function CWE-749

How to fix

Remediation Available

hybrid backup syncNVD

Affected:< 3.0.210506Fixed in:3.0.210506CVE-2021-28809derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploit Intelligence

15.80%probability of exploitation in 30 days

97thpercentile

Very high risk: more likely to be exploited than 97% of all known CVEs.

References

Vendor Advisory1

qnap.com

Third-Party Advisory1

zerodayinitiative.com

Related Vulnerabilities

Other CWE-284 (Improper Access Control) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-27350	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2019-1653	High	7.5	100%	KEV	-
CVE-2023-23752	Medium	5.3	100%	KEV	Fix
CVE-2023-38205	High	7.5	100%	KEV	-
CVE-2023-29298	High	7.5	100%	KEV	-
CVE-2024-27348	Critical	9.8	99%	KEV	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.