CVE-2021-27477

PLC execution stop via malformed FL-net frame

Published Jul 1, 2021 · Updated Aug 3, 2024

An out-of-bounds write in JTEKT TOYOPUC PLC modules allows attackers to stop PLC execution via a crafted FL-net message frame. The FL-net message handler accepts an intentionally malformed frame and writes past the receive buffer, causing the CPU to detect a system error. Access to the factory FL-net network is required, and recovery from the stopped program requires a PLC reset or power cycle.

CVSS severity6.5
Medium
EPSS probability1.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

An out-of-bounds write in JTEKT TOYOPUC PLC modules allows attackers to stop PLC execution via a crafted FL-net message frame. The FL-net message handler accepts an intentionally malformed frame and writes past the receive buffer, causing the CPU to detect a system error. Access to the factory FL-net network is required, and recovery from the stopped program requires a PLC reset or power cycle.

The record

CVE
CVE-2021-27477
Published
Jul 1, 2021
Updated
Aug 3, 2024
Vendor
JTEKT Corporation
Product
TOYOPUC PLC
Classifications
CWE-119, T0814
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=The following versions of the PLC are affected: PC10G-CPU, 2PORT-EFR, Plus CPU, Plus EX, Plus EX2, Plus EFR, Plus EFR2, Plus 2P-EFR, PC10P-DP, PC10P-DP-IO, Plus BUS-EX, Nano 10GX, Nano 2ET,PC10PE, PC10PE-16/16P, PC10E, FL/ET-T-V2H, PC10B,PC10B-P, Nano CPU, PC10P, PC10GE.

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

JTEKT Corporation · TOYOPUC PLCversion=The following versions of the PLC are affected: PC10G-CPU, 2PORT-EFR, Plus CPU, Plus EX, Plus EX2, Plus EFR, Plus EFR2, Plus 2P-EFR, PC10P-DP, PC10P-DP-IO, Plus BUS-EX, Nano 10GX, Nano 2ET,PC10PE, PC10PE-16/16P, PC10E, FL/ET-T-V2H, PC10B,PC10B-P, Nano CPU, PC10P, PC10GE.

Published CVSS scores

6.5JTEKT CorporationCVSS:3.0/AV:A/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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T0814Denial of Service

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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