CVE-2021-20597Network attack vector

Unauthorized login via sniffed credential exchanges

Published Aug 6, 2021 · Updated Aug 3, 2024

Credential exposure in Mitsubishi Electric MELSEC iQ-R Safety and SIL2 Process CPUs allows remote attackers to obtain login access. The firmware insufficiently protects reusable credentials during user registration and password changes, allowing network-traffic sniffing to capture them. The attacker must observe the relevant exchange; affected Safety CPU firmware is 26 and earlier, while affected SIL2 Process CPU firmware is 11 and earlier.

CVSS severity9.1
Critical
EPSS probability2.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Credential exposure in Mitsubishi Electric MELSEC iQ-R Safety and SIL2 Process CPUs allows remote attackers to obtain login access. The firmware insufficiently protects reusable credentials during user registration and password changes, allowing network-traffic sniffing to capture them. The attacker must observe the relevant exchange; affected Safety CPU firmware is 26 and earlier, while affected SIL2 Process CPU firmware is 11 and earlier.

The record

CVE
CVE-2021-20597
Published
Aug 6, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-522, T1040, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 6, 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

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.1National Institute of Standards and TechnologyCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
6.4National Institute of Standards and TechnologyAV:N/AC:L/Au:N/C:P/I:P/A:N

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-522Insufficiently Protected Credentials
T1040Network Sniffing
T1078Valid Accounts

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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