CVE-2021-21962Public exploitNetwork attack vector

Remote code execution via unbounded update-payload unescape

Published Feb 4, 2022 · Updated Apr 15, 2025

Heap-based buffer overflow in SeaConnect 370W 1.3.34 allows remote attackers to execute code through crafted MQTT update messages. ParseToDownloadMessage allocates at most 256 bytes, then unescape copies the full quote-escaped payload without enforcing that limit. The attacker must intercept the device's SeaCloud MQTTS connection and inject a u-download command; successful corruption permits arbitrary instruction execution.

CVSS severity9.0
Critical
EPSS probability2.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in SeaConnect 370W 1.3.34 allows remote attackers to execute code through crafted MQTT update messages. ParseToDownloadMessage allocates at most 256 bytes, then unescape copies the full quote-escaped payload without enforcing that limit. The attacker must intercept the device's SeaCloud MQTTS connection and inject a u-download command; successful corruption permits arbitrary instruction execution.

The record

CVE
CVE-2021-21962
Published
Feb 4, 2022
Updated
Apr 15, 2025
Vendor
Sealevel Systems, Inc.
Product
SeaConnect 370W
Classifications
CWE-122, CWE-787, T1203, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 4, 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=Sealevel Systems, Inc. SeaConnect 370W v1.3.34

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

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

Published CVSS scores

8.1NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
9.0Cisco TalosCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-122Heap-based Buffer Overflow
CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution
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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