CVE-2022-40267Public exploitNetwork attack vector

Authentication bypass via predictable session identifiers

Published Jan 20, 2023 · Updated Aug 3, 2024

Authentication bypass in Mitsubishi Electric MELSEC iQ-F and iQ-R PLC web servers allows remote attackers to obtain a valid session. The random-buffer generator reseeds a linear congruential generator with prior output, while an unauthenticated endpoint exposes values that reveal seeds for future session identifiers. Exploitation requires the Web server function and a subsequent legitimate login before a predicted identifier becomes valid, granting unauthorized web-server access.

CVSS severity5.9
Medium
EPSS probability1.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Mitsubishi Electric MELSEC iQ-F and iQ-R PLC web servers allows remote attackers to obtain a valid session. The random-buffer generator reseeds a linear congruential generator with prior output, while an unauthenticated endpoint exposes values that reveal seeds for future session identifiers. Exploitation requires the Web server function and a subsequent legitimate login before a predicted identifier becomes valid, granting unauthorized web-server access.

The record

CVE
CVE-2022-40267
Published
Jan 20, 2023
Updated
Aug 3, 2024
Vendor
Mitsubishi Electric Corporation
Product
MELSEC iQ-R Series R16ENCPU
Classifications
CWE-337, CWE-335, T1550.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 20, 2023CVE 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=versions 66 and prior

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mitsubishi Electric Corporation · MELSEC iQ-R Series R16ENCPUversion=versions 66 and prior
Mitsubishi Electric Corporation · FX5S-40MR/ESversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series CPU Module FX5UC-32MT/DS-TSversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-60MR/ES-Aversion=1.043 and prior
Mitsubishi Electric Corporation · FX5UJ-60MR/ES Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5UJ-24MT/ES Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-R Series R32CPUversion=versions 66 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-64MR/ESversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-R Series R16CPUversion=versions 66 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-60MT/ESversion=1.003 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-32MT/DSSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · FX5S-40MT/ESSversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-80MR/ESversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-40MT/ESversion=1.003 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-30MT/ESSversion=1.003 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-64MT/DSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-32MT/ESSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · R16CPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-60MR/ESversion=1.003 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series CPU module FX5U-80MT/DSSversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UC-32MT/Dversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series CPU module FX5U-32MT/DSSversion=0 <=1.042
Mitsubishi Electric Corporation · FX5S-60MR/ESversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-64MT/DSSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · FX5UC-96MT/DSS Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · R32CPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-60MR/ESversion=1.042 and prior
Mitsubishi Electric Corporation · R120CPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · R120ENCPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · R04ENCPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · R04CPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-80MT/ESSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · FX5UC-96MT/D Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-32MR/DSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-40MT/ESversion=1.042 and prior
Mitsubishi Electric Corporation · FX5UJ-24MT/ESS Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5S-60MT/ESversion=0 <=1.042
Mitsubishi Electric Corporation · R00CPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series CPU Module FX5UC-32MT/DSSversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-60MT/ESSversion=1.003 and prior
Mitsubishi Electric Corporation · FX5S-30MR/ESversion=0 <=1.042
Mitsubishi Electric Corporation · R16ENCPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-24MT/ESSversion=1.042 and prior
Mitsubishi Electric Corporation · MELSEC iQ-R Series R00CPUversion=versions 33 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series CPU module FX5U-80MT/ESSversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-80MT/DSSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · FX5UJ-40MT/ES Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5UJ-24MT/ES-A Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series CPU module FX5UC-32MR/DS-TSversion=0 <=1.042
Mitsubishi Electric Corporation · FX5S-80MT/ESversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-40MR/ESversion=1.003 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UC-32MT/DSSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-32MR/ESversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-64MT/ESSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-60MT/ES-Aversion=1.043 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series CPU module FX5U-64MT/DSSversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-32MT/ESversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-40MT/ESSversion=1.003 and prior
Mitsubishi Electric Corporation · FX5UJ-40MT/ES-A Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-64MR/DSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · R08CPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5UJ-40MT/ESS Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-60MT/ESversion=1.042 and prior
Mitsubishi Electric Corporation · MELSEC iQ-R Series R04ENCPUversion=versions 66 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-30MT/ESversion=1.003 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-80MT/ESversion=1.003 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-24MR/ES-Aversion=1.043 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series CPU module FX5UC-32MT/Dversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-R Series R08ENCPUversion=versions 66 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UC-64MT/Dversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UC-32MR/DS-TSversion=versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-R Series R32ENCPUversion=versions 66 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-24MT/ES-Aversion=1.043 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-40MR/ESversion=1.042 and prior
Mitsubishi Electric Corporation · MELSEC iQ-R Series R08CPUversion=versions 66 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-32MT/DSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · FX5UJ-60MT/ESS Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-80MT/DSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-60MT/ESSversion=1.042 and prior
Mitsubishi Electric Corporation · FX5S-40MT/ESversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UC-64MT/DSSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-R Series R04CPUversion=versions 66 and prior
Mitsubishi Electric Corporation · FX5UJ-60MT/ES-A Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UC-32MT/DS-TSversion=versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-80MT/ESSversion=1.003 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-80MR/DSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · FX5S-30MT/ESSversion=0 <=1.042
Mitsubishi Electric Corporation · FX5S-80MR/ESversion=0 <=1.042
Mitsubishi Electric Corporation · FX5S-30MT/ESversion=0 <=1.042
Mitsubishi Electric Corporation · FX5UC-64MT/DSS Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5UJ-40MR/ES Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5UJ-24MR/ES-A Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5S-60MT/ESSversion=0 <=1.042
Mitsubishi Electric Corporation · FX5UJ-60MT/ES Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5UC-32MT/DSS-TS Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-40MR/ES-Aversion=1.043 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UC-96MT/Dversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5U-64MT/ESversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · R01CPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-R Series R01CPUversion=versions 33 and prior
Mitsubishi Electric Corporation · R08ENCPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-24MR/ESversion=1.042 and prior
Mitsubishi Electric Corporation · FX5UC-64MT/D Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-R Series R120ENCPUversion=versions 66 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-40MT/ESSversion=1.042 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-30MR/ESversion=1.003 and prior
Mitsubishi Electric Corporation · FX5UJ-24MR/ES Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5UJ-60MR/ES-A Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · FX5S-80MT/ESSversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-24MT/ESversion=1.042 and prior
Mitsubishi Electric Corporation · FX5UJ-40MR/ES-A Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UC-96MT/DSSversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · FX5U-80MT/ESversion=serial number 179**** and prior, and versions 1.074 and prior; version=serial number 17X**** or later, and versions 1.280 and prior
Mitsubishi Electric Corporation · R32ENCPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · R02CPU Firmwareversion=0 <=1.042
Mitsubishi Electric Corporation · MELSEC iQ-R Series R02CPUversion=versions 33 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UC-32MT/DSS-TSversion=versions 1.280 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5UJ-40MT/ES-Aversion=1.043 and prior
Mitsubishi Electric Corporation · MELSEC iQ-F Series FX5S-80MR/ESversion=1.003 and prior
Mitsubishi Electric Corporation · MELSEC iQ-R Series R120CPUversion=versions 66 and prior

Published CVSS scores

9.1NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
5.9Mitsubishi Electric CorporationCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
7.1Cisco TalosCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/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.

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-337Predictable Seed in Pseudo-Random Number Generator (PRNG)
CWE-335Incorrect Usage of Seeds in Pseudo-Random Number Generator (PRNG)
T1550.004Web Session Cookie

Public exploit references

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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