CVE-2021-28816

HIGHNVD 7.67.6—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.6 under NVD CVSS v3. EPSS exploit probability: 1.2%, top 21% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
7.6
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.6Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

A stack buffer overflow vulnerability has been reported to affect QNAP device running QTS, QuTScloud, QuTS hero. If exploited, this vulnerability allows attackers to execute arbitrary code. We have already fixed this vulnerability in the following versions of QTS, QuTScloud, QuTS hero: QTS 4.5.4.1715 build 20210630 and later QTS 5.0.0.1716 build 20210701 and later QTS 4.3.3.1693 build 20210624 and later QTS 4.3.6.1750 build 20210730 and later QuTScloud c4.5.6.1755 and later QuTS hero h4.5.4.1771 build 20210825 and later

CVSS v3
7.6
EG Score
7.6(medium)
EPSS
56.5%
KEV
Not listed

Published

September 10, 2021

Last Modified

November 21, 2024

References (2)

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-16 17:00 UTCEPSS rescore
  2. 2026-07-15 16:55 UTCEPSS rescore
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  1. 2026-06-29 14:04 UTCEPSS rescore
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  7. 2026-06-25 13:48 UTCEPSS rescore
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  11. 2026-06-23 21:31 UTCEPSS rescore
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  21. 2026-06-18 17:51 UTCEPSS rescore
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  41. 2026-06-05 06:09 UTCEPSS rescore
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  45. 2026-06-02 20:11 UTCEPSS rescore
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  48. 2026-06-01 13:50 UTCEPSS rescore
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  50. 2026-05-31 22:29 UTCEPSS rescore
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  52. 2026-05-31 00:15 UTCEPSS rescore
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  58. 2026-05-26 13:42 UTCEPSS rescore
  59. 2026-05-26 10:35 UTCEG score recompute
  60. 2026-05-26 10:35 UTCGHSA enrichment
  61. 2026-05-26 07:17 UTCEPSS rescore
  62. 2026-05-26 07:17 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-28816?
CVE-2021-28816 is a high vulnerability published on September 10, 2021. A stack buffer overflow vulnerability has been reported to affect QNAP device running QTS, QuTScloud, QuTS hero. If exploited, this vulnerability allows attackers to execute arbitrary code. We have already fixed this vulnerability in the following versions of QTS, QuTScloud, QuTS hero: QTS…
When was CVE-2021-28816 disclosed?
CVE-2021-28816 was first published in the National Vulnerability Database on September 10, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-28816 actively exploited?
CVE-2021-28816 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 56.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-28816?
CVE-2021-28816 has a CVSS v3 base score of 7.6 (NVD).
How do I remediate CVE-2021-28816?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-28816, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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