How severe is CVE-2021-27477?

CVE-2021-27477 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-27477 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27477?

CVE-2021-27477 primarily affects Jtekt Pc10g-cpu Firmware. In total, 22 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-27477?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-27477 published?

CVE-2021-27477 was published on 2021-07-01 and last updated on 2026-06-17.

CVE-2021-27477

CVE-2021-27477 is a high-severity vulnerability in Jtekt Pc10g-cpu Firmware with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 7.8
EPSS exploit prediction: 1% (62nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Jtekt Pc10g-cpu Firmware
Published: 2021-07-01
Last modified: 2026-06-17

Description

When JTEKT Corporation TOYOPUC PLC versions 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, and PC10GE receive an invalid frame, the outside area of a receive buffer for FL-net are overwritten. As a result, the PLC CPU detects a system error, and the affected products stop.

Frequently asked questions

What is CVE-2021-27477?: When JTEKT Corporation TOYOPUC PLC versions 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, and PC10GE receive an invalid frame, the outside area of a receive buffer for FL-net are overwritten. As a result, the PLC CPU detects a system error, and the affected products stop.
How severe is CVE-2021-27477?: CVE-2021-27477 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-27477 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27477?: CVE-2021-27477 primarily affects Jtekt Pc10g-cpu Firmware. In total, 22 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-27477?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-27477 published?: CVE-2021-27477 was published on 2021-07-01 and last updated on 2026-06-17.

References

https://us-cert.cisa.gov/ics/advisories/icsa-21-180-04

Affected products (22)

cpe:2.3:o:jtekt:pc10g-cpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:2port-efr_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:plus_cpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:plus_ex_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:plus_ex2_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:plus_efr_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:plus_efr2_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:plus_2p-efr_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:pc10p-dp_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:pc10p-dp-io_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:plus_bus-ex_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:nano_10gx_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:nano_2et_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:pc10pe_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:pc10pe-16\/16p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:pc10e_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:fl\/et-t-v2h_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:pc10b_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:pc10b-p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:nano_cpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:pc10p_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:jtekt:pc10ge_firmware:*:*:*:*:*:*:*:*

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