CVE-2021-21964Public exploitNetwork attack vector

Service interruption via unauthenticated Modbus reboot command

Published Feb 4, 2022 · Updated Apr 15, 2025

Improper access control in SeaConnect 370W 1.3.34 allows remote attackers to reboot the device through an unauthenticated Modbus request. DispatchModbusRequest routes proprietary function code 0x13 directly to the Reboot routine without authenticating the sender. Modbus TCP must be enabled, after which repeated requests on TCP port 502 can keep the edge module unavailable.

CVSS severity7.4
High
EPSS probability0.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in SeaConnect 370W 1.3.34 allows remote attackers to reboot the device through an unauthenticated Modbus request. DispatchModbusRequest routes proprietary function code 0x13 directly to the Reboot routine without authenticating the sender. Modbus TCP must be enabled, after which repeated requests on TCP port 502 can keep the edge module unavailable.

The record

CVE
CVE-2021-21964
Published
Feb 4, 2022
Updated
Apr 15, 2025
Vendor
Sealevel Systems, Inc.
Product
SeaConnect 370W
Classifications
CWE-306, CWE-284, T1529
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

7.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:H
7.1NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:C
8.6Cisco TalosCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

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-306Missing Authentication for Critical Function
CWE-284Improper Access Control
T1529System Shutdown/Reboot

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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