CVE-2021-37400

PLC program manipulation via exposed transport credentials

Published Dec 28, 2021 · Updated Aug 4, 2024

Unprotected credential transport in IDEC PLCs and programming software allows adjacent attackers to intercept PLC user credentials. The PLC-to-software protocol transmits authentication information with insufficient protection, exposing it in captured communication data. An unauthenticated attacker positioned on the adjacent network can use the credentials to read, rewrite, upload, or download PLC programs.

CVSS severity7.6
High
EPSS probability1.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unprotected credential transport in IDEC PLCs and programming software allows adjacent attackers to intercept PLC user credentials. The PLC-to-software protocol transmits authentication information with insufficient protection, exposing it in captured communication data. An unauthenticated attacker positioned on the adjacent network can use the credentials to read, rewrite, upload, or download PLC programs.

The record

CVE
CVE-2021-37400
Published
Dec 28, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-523, T1040
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 28, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.6JPCERT/CCCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
7.6IDEC CorporationCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-523Unprotected Transport of Credentials
T1040Network Sniffing

Public exploit references

No public exploit references are available in this record.

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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