CVE-2021-21967Public exploitNetwork attack vector

Device crash via unterminated OTA destination

Published Apr 14, 2022 · Updated Apr 15, 2025

Stack-based buffer overflow in Sealevel SeaConnect 370W 1.3.34 allows man-in-the-middle attackers to crash it via an MQTT OTA message. ParseToDownloadMessage copies up to 255 bytes of the JSON dest value into a 64-byte field, leaving it unterminated; SeaConnectOTADownload_file then uses strcpy on that field and overwrites stack state. Triggering the crash requires interception and modification of MQTTS update traffic between the device and SeaCloud; the reported consequence is a device crash.

CVSS severity6.5
Medium
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in Sealevel SeaConnect 370W 1.3.34 allows man-in-the-middle attackers to crash it via an MQTT OTA message. ParseToDownloadMessage copies up to 255 bytes of the JSON dest value into a 64-byte field, leaving it unterminated; SeaConnectOTADownload_file then uses strcpy on that field and overwrites stack state. Triggering the crash requires interception and modification of MQTTS update traffic between the device and SeaCloud; the reported consequence is a device crash.

The record

CVE
CVE-2021-21967
Published
Apr 14, 2022
Updated
Apr 15, 2025
Vendor
Sealevel Systems, Inc.
Product
SeaConnect 370W
Classifications
CWE-120, T1499.004, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 14, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 15, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=v1.3.34

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Sealevel Systems, Inc. · SeaConnect 370Wversion=v1.3.34

Published CVSS scores

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
6.5Cisco TalosCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
7.1NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
T1499.004Application or System Exploitation
T1557Adversary-in-the-Middle

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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