CVE-2021-40334Network attack vector

Remote communications disruption via SSH activation

Published Dec 2, 2021 · Updated Sep 16, 2024

Missing-handler flaw in Hitachi Energy XMC20 and FOX61x before R15A allows remote attackers to disrupt NMS-to-NE communications. The proprietary management protocol on TCP port 5558 mishandles SSH activation, causing the management channel between the NMS and network element to fail. Exploitation is unauthenticated and network-reachable; the reported consequence is a communications interruption, not data access or modification.

CVSS severity8.6
High
EPSS probability0.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing-handler flaw in Hitachi Energy XMC20 and FOX61x before R15A allows remote attackers to disrupt NMS-to-NE communications. The proprietary management protocol on TCP port 5558 mishandles SSH activation, causing the management channel between the NMS and network element to fail. Exploitation is unauthenticated and network-reachable; the reported consequence is a communications interruption, not data access or modification.

The record

CVE
CVE-2021-40334
Published
Dec 2, 2021
Updated
Sep 16, 2024
Vendor
Hitachi Energy
Product
XMC20
Classifications
CWE-431, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 2, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record 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=R15A <R15A

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Hitachi Energy · XMC20version=R15A <R15A
Hitachi Energy · FOX61xversion=R15A <R15A

Published CVSS scores

8.6Hitachi EnergyCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-431Missing Handler
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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