CVE-2021-38691

HIGHNVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 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
8.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 8.1Exploit: 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 QVR Elite, QVR Pro, QVR Guard. If exploited, this vulnerability allows attackers to execute arbitrary code. We have already fixed this vulnerability in the following versions of QVR Elite, QVR Pro, QVR Guard: QuTS hero h5.0.0: QVR Elite 2.1.4.0 (2021/12/06) and later QuTS hero h4.5.4: QVR Elite 2.1.4.0 (2021/12/06) and later QTS 5.0.0: QVR Elite 2.1.4.0 (2021/12/06) and later QTS 4.5.4: QVR Elite 2.1.4.0 (2021/12/06) and later QTS 4.5.4: QVR Pro 2.1.3.0 (2021/12/06) and later QTS 5.0.0: QVR Pro 2.1.3.0 (2021/12/06) and later QTS 4.5.4: QVR Guard 2.1.3.0 (2021/12/06) and later QTS 5.0.0: QVR Guard 2.1.3.0 (2021/12/06) and later

CVSS v3
8.1
EG Score
8.1(medium)
EPSS
67.1%
KEV
Not listed

Published

January 14, 2022

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 10× in last 7d / 41× 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. 2026-07-16 17:00 UTCEPSS rescore
  3. 2026-07-15 16:55 UTCEPSS rescore
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  1. 2026-06-28 04:54 UTCEPSS rescore
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  7. 2026-06-23 21:31 UTCEPSS rescore
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  9. 2026-06-21 14:55 UTCEPSS rescore
  10. 2026-06-21 01:58 UTCEPSS rescore
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  12. 2026-06-19 19:24 UTCEPSS rescore
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  20. 2026-06-14 23:15 UTCEPSS rescore
  21. 2026-06-13 22:58 UTCEPSS rescore
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  23. 2026-06-12 23:10 UTCEPSS rescore
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  25. 2026-06-11 13:58 UTCEPSS rescore
  26. 2026-06-10 22:16 UTCEPSS rescore
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  40. 2026-06-02 20:11 UTCEPSS rescore
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  42. 2026-06-01 13:50 UTCEPSS rescore
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  44. 2026-05-31 22:29 UTCEPSS rescore
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  46. 2026-05-31 00:15 UTCEPSS rescore
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  48. 2026-05-29 13:42 UTCEPSS rescore
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  50. 2026-05-28 13:43 UTCEPSS rescore
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  52. 2026-05-27 13:39 UTCEPSS rescore
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  56. 2026-05-26 07:17 UTCEPSS rescore
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  58. 2026-05-26 07:17 UTCEPSS rescore
  59. 2026-05-26 04:49 UTCEG score recompute
  60. 2026-05-26 04:49 UTCGHSA enrichment
  61. 2026-05-25 20:46 UTCOSV refresh

Frequently asked(5)

What is CVE-2021-38691?
CVE-2021-38691 is a high vulnerability published on January 14, 2022. A stack buffer overflow vulnerability has been reported to affect QNAP device running QVR Elite, QVR Pro, QVR Guard. If exploited, this vulnerability allows attackers to execute arbitrary code. We have already fixed this vulnerability in the following versions of QVR Elite, QVR Pro, QVR Guard: QuTS…
When was CVE-2021-38691 disclosed?
CVE-2021-38691 was first published in the National Vulnerability Database on January 14, 2022, 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-2021-38691 actively exploited?
CVE-2021-38691 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 67.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-38691?
CVE-2021-38691 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2021-38691?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-38691, 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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