CVE-2021-21962: A heap-based buffer overflow vulnerability exists in the OTA Update u-download functionality of Sealevel Syste

This week

HIGH 8.1REMOTEMITIGATE

CVE-2021-21962 is a high-severity flaw (CVSS 8.1) affecting seaconnect 370w firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A heap-based buffer overflow vulnerability exists in the OTA Update u-download functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. A series of specially-crafted MQTT payloads can lead to remote code execution. An attacker must perform a man-in-the-middle attack in order to trigger this vulnerability.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	2.0% (top 19%)
CISA exploited list	No
Weakness	CWE-122, CWE-787
Published	2022-02-04
Last modified	2026-06-17

Publisher (CNA): Talos · Vendor: sealevel

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-02-04 23:15 UTCPublished CVE record published
2026-06-17 03:36 UTCUpdated Record last modified

sealevel seaconnect 370w firmware MITIGATE

Affected: 1.3.34

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.3.34

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-21962?

seaconnect 370w firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-21962 being exploited?

CVE-2021-21962 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-21962 affect?

CVE-2021-21962 affects seaconnect 370w firmware. Severity is high (CVSS 8.1). A heap-based buffer overflow vulnerability exists in the OTA Update u-download functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. A series of specially-crafted MQTT payloads can lead to remote code execution. An attacker must

How urgent is CVE-2021-21962?

Priority 59/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

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CVE-2021-21968 HIGH 8.3 MITIGATE A file write vulnerability exists in the OTA update task functionality of Sealevel Systems, Inc
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References

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