No exploitation reportedFix available

CVE-2021-34343

Q: Is CVE-2021-34343 actively exploited?

Active exploitation of CVE-2021-34343 has not been confirmed. Its EPSS score was 2.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-34343?

CVE-2021-34343 has a CVSS v3 base score of 7.2 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2021-09-10
Fixed in5.0.0.1716 · 4.5.4.1715 · 4.3.6.1750 · 4.3.3.1693
WeaknessCWE-787

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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 QuTScloud c4.5.6.1755 and later QuTS hero h4.5.4.1771 build 20210825 and later

Timeline

dates in UTC

2021-09-1004:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-34343?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-34343?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Qnap qts

Branch	Affected	Fixed in	Source
5.0	≥ 5.0.0, < 5.0.0.1716	5.0.0.1716	NVD
4.x	≥ 4.4.0, < 4.5.4.1715	4.5.4.1715	NVD
4.3	≥ 4.3.4, < 4.3.6.1750	4.3.6.1750	NVD
4.3	< 4.3.3.1693	4.3.3.1693	NVD

Qnap quts hero

Branch	Affected	Fixed in	Source
—	< h4.5.4.1771	h4.5.4.1771	NVD

Qnap qutscloud

Branch	Affected	Fixed in	Source
—	< c4.5.6.1755	c4.5.6.1755	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Qnap qts to 5.0.0.1716 · 4.5.4.1715 · 4.3.6.1750 · 4.3.3.1693

Advisories and patches

www.qnap.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CNACVSS 3.16read 2026-10-23
NVDCVSS 3.17.2read 2026-10-23
NVDCVSS 2.06.5read 2026-10-23
CNAweakness (CWE)CWE-787read 2026-10-23
NVDweakness (CWE)CWE-787read 2026-10-23
FIRST EPSSEPSS score2.0 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Published: 2021-09-10
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-34343?

Is CVE-2021-34343 actively exploited?

Active exploitation of CVE-2021-34343 has not been confirmed. Its EPSS score was 2.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-34343?

CVE-2021-34343 has a CVSS v3 base score of 7.2 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.

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