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No exploitation reported

CVE-2021-20594

No exploitation reported by the sources we read.

  • Published2021-08-06
  • WeaknessCWE-200

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Mitsubishi Electric MELSEC iQ-R series Safety CPU modules R08/16/32/120SFCPU firmware versions "26" and prior and Mitsubishi Electric MELSEC iQ-R series SIL2 Process CPU modules R08/16/32/120PSFCPU firmware versions "11" and prior allows a remote unauthenticated attacker to acquire legitimate user names registered in the module via brute-force attack on user names.

Timeline

dates in UTC
  1. 2021-08-0617:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-20594?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-20594?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Mitsubishielectric r08psfcpu firmwareversion to verify
BranchAffectedFixed in
—all versionsno fix published
Mitsubishielectric r08sfcpu firmwareversion to verify
BranchAffectedFixed in
—all versionsno fix published
Mitsubishielectric r120psfcpu firmwareversion to verify
BranchAffectedFixed in
—all versionsno fix published

5 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • ICSA-21-250-01 CISA8 known affected

    Mitsubishi Electric MELSEC iQ-R Series

    Mitsubishi Electric Corporation MELSEC iQ-R series Safety CPU R08SFCPU Firmware: <=26 · Mitsubishi Electric Corporation MELSEC iQ-R series Safety CPU R16SFCPU Firmware: <=26 · Mitsubishi Electric Corporation MELSEC iQ-R series Safety CPU R32SFCPU Firmware: <=26 · +5 more

Full record on NVD

Fix

  1. Mitigation from the vendor CISA ICSA-21-250-01 · 8 productsUsers of the affected products and versions may take measures through mitigations and workarounds. Mitsubishi Electric has released the fixed versions for CVE-2021-20594 and CVE-2021-20597 as shown below, but updating the product to the fixed version is not available.
  2. Mitigation from the vendor CISA ICSA-21-250-01 · 8 productsMELSEC iQ-R series Safety CPU R08/16/32/120SFCPU:Firmware versions "27" or later
  3. Mitigation from the vendor CISA ICSA-21-250-01 · 8 productsMELSEC iQ-R series SIL2 Process CPU R08/16/32/120PSFCPU:Firmware versions "12" or later
  4. Mitigation from the vendor CISA ICSA-21-250-01 · 8 productsMitsubishi Electric recommends users take the following mitigation measures to minimize the risk of exploiting these vulnerabilities:
  5. Mitigation from the vendor CISA ICSA-21-250-01 · 8 productsUse a firewall or virtual private network (VPN), etc. to prevent unauthorized access when Internet access is required.
  6. Mitigation from the vendor CISA ICSA-21-250-01 · 8 productsUse within a LAN and block access from untrusted networks and hosts through firewalls.

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • NVDCVSS 3.17.5read 2026-10-23
  • NVDCVSS 2.05read 2026-10-23
  • NVDweakness (CWE)CWE-200read 2026-10-23
  • FIRST EPSSEPSS score2.4 %2026-10-22

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Published
2021-08-06
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-20594?

Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Mitsubishi Electric MELSEC iQ-R series Safety CPU modules R08/16/32/120SFCPU firmware versions "26" and prior and Mitsubishi Electric MELSEC iQ-R series SIL2 Process CPU modules R08/16/32/120PSFCPU firmware versions "11" and prior allows a remote unauthenticated attacker to acquire legitimate user names registered in the module via brute-force attack on user names.

Is CVE-2021-20594 actively exploited?

Active exploitation of CVE-2021-20594 has not been confirmed. Its EPSS score was 2.4% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-20594?

CVE-2021-20594 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

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