CVE-2021-21960: A stack-based buffer overflow vulnerability exists in both the LLMNR functionality of Sealevel Systems, Inc

This week

CRITICAL 10.0REMOTEMITIGATE

CVE-2021-21960 is a critical-severity flaw (CVSS 10.0) affecting seaconnect 370w firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A stack-based buffer overflow vulnerability exists in both the LLMNR functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. A specially-crafted network packet can lead to remote code execution. An attacker can send a malicious packet to trigger this vulnerability.

Why this priority

Critical 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	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.6% (top 14%)
CISA exploited list	No
Weakness	CWE-121, CWE-1284
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-2021-21960?

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

Is CVE-2021-21960 being exploited?

CVE-2021-21960 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-2021-21960 affect?

CVE-2021-21960 affects seaconnect 370w firmware. Severity is critical (CVSS 10.0). A stack-based buffer overflow vulnerability exists in both the LLMNR functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. A specially-crafted network packet can lead to remote code execution. An attacker can send a malicious pac

How urgent is CVE-2021-21960?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

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CVE-2021-21970 HIGH 8.1 MITIGATE An out-of-bounds write vulnerability exists in the HandleSeaCloudMessage functionality of Sealevel Systems, In
CVE-2021-21969 HIGH 8.1 MITIGATE An out-of-bounds write vulnerability exists in the HandleSeaCloudMessage functionality of Sealevel Systems, In
CVE-2021-21968 HIGH 8.3 MITIGATE A file write vulnerability exists in the OTA update task functionality of Sealevel Systems, Inc
CVE-2021-21967 MEDIUM 5.9 MITIGATE An out-of-bounds write vulnerability exists in the OTA update task functionality of Sealevel Systems, Inc

References

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