CVE-2021-21971

mediumpriority · track · 24EPSS 0.007 · 53 %ileEUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.70% (53rd) EPSS

CVSS 4.3 · medium

Is it mine?

2 products

Check your exposure

Who says so?

3 sources

cnnvd · enisa_euvd · nvd

EPSS · scored 2026-10-27

An out-of-bounds write vulnerability exists in the URL_decode functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. A specially-crafted MQTT payload can lead to an out-of-bounds write. An attacker can perform a man-in-the-middle attack to trigger this vulnerability.

cvss

Technical severity, 0–10. One row per scoring source.

5.9

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · low–medium · 3.7–5.9

v2.04.3mediumAV:N/AC:M/Au:N/C:N/I:P/A:Nprimary · NVD / NIST USexploitability 8.6 · impact 2.9

v3.15.9mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:Nprimary · NVD / NIST USexploitability 2.2 · impact 3.6

v3.03.7lowCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:Nsecondary · ENISA EU

v3.03.7lowCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:Nsecondary · talos-cna@cisco.com USexploitability 2.2 · impact 1.4

v3.15.4mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-787USprimary

affected products (2)

Products and version ranges known to be affected.

n/a Sealevel≤ Sealevel Systems, Inc. SeaConnect 370W v1.3.34enisa_euvdEU
sealevel seaconnect 370w firmware= 1.3.34nvdUScpe:2.3:o:sealevel:seaconnect_370w_firmware:*:*:*:*:*:*:*:*

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd nvd NVD CVE.org MITRE

published 2022-02-04modified 2026-06-17

related (16,125)

Related entries.

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In the Linux kernel, the following vulnerability has been resolved: ipv6: account for fraggap on the paged allocation path In __ip6_append_data(), when the paged-allocation branc…
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In the Linux kernel, the following vulnerability has been resolved: netfilter: bridge: make ebt_snat ARP rewrite writable The ebtables SNAT target keeps the Ethernet source addre…
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+16120 more

references (7)

External citations — patches, advisories, analysis.

https://nvd.nist.gov/vuln/detail/CVE-2021-21971 cnnvd
https://talosintelligence.com/vulnerability_reports/TALOS-2021-1397 cnnvd
https://talosintelligence.com/vulnerability_reports/TALOS-2021-1406 cnnvd
https://www.sealevel.com/Patchcnnvd
https://talosintelligence.com/vulnerability_reports/TALOS-2021-1406 enisa_euvd
https://talosintelligence.com/vulnerability_reports/TALOS-2021-1397ExploitTechnical DescriptionThird Party Advisorynvd
https://talosintelligence.com/vulnerability_reports/TALOS-2021-1406Not ApplicableThird Party Advisorynvd

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