How severe is CVE-2021-20599?

CVE-2021-20599 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-20599 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20599?

CVE-2021-20599 primarily affects Mitsubishielectric R08sfcpu Firmware. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20599?

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

When was CVE-2021-20599 published?

CVE-2021-20599 was published on 2021-10-14 and last updated on 2026-06-17.

CVE-2021-20599

CVE-2021-20599 is a critical-severity vulnerability in Mitsubishielectric R08sfcpu Firmware with a CVSS 3.x base score of 9.1. 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-319.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v2: 5.0
EPSS exploit prediction: 1% (67th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-319
Affected product: Mitsubishielectric R08sfcpu Firmware
Published: 2021-10-14
Last modified: 2026-06-17

Description

Cleartext Transmission of Sensitive InformationCleartext transmission of sensitive information vulnerability in MELSEC iQ-R series Safety CPU R08/16/32/120SFCPU firmware versions "26" and prior and MELSEC iQ-R series SIL2 Process CPU R08/16/32/120PSFCPU firmware versions "11" and prior allows a remote unauthenticated attacker to login to a target CPU module by obtaining credentials other than password.

Frequently asked questions

What is CVE-2021-20599?: Cleartext Transmission of Sensitive InformationCleartext transmission of sensitive information vulnerability in MELSEC iQ-R series Safety CPU R08/16/32/120SFCPU firmware versions "26" and prior and MELSEC iQ-R series SIL2 Process CPU R08/16/32/120PSFCPU firmware versions "11" and prior allows a remote unauthenticated attacker to login to a target CPU module by obtaining credentials other than password.
How severe is CVE-2021-20599?: CVE-2021-20599 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-20599 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20599?: CVE-2021-20599 primarily affects Mitsubishielectric R08sfcpu Firmware. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20599?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-20599 published?: CVE-2021-20599 was published on 2021-10-14 and last updated on 2026-06-17.

References

Affected products (8)

cpe:2.3:o:mitsubishielectric:r08sfcpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:mitsubishielectric:r16sfcpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:mitsubishielectric:r32sfcpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:mitsubishielectric:r120sfcpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:mitsubishielectric:r08psfcpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:mitsubishielectric:r16psfcpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:mitsubishielectric:r32psfcpu_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:mitsubishielectric:r120psfcpu_firmware:*:*:*:*:*:*:*:*

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