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CVE-2022-40267: Authentication Bypass Vulnerability in Web Server Function on MELSEC Series

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-01-20 · updated 2026-06-17
• Weakness: CWE-337

Description

Predictable Seed in Pseudo-Random Number Generator (PRNG) vulnerability in Mitsubishi Electric Corporation MELSEC iQ-F Series FX5U-xMy/z (x=32,64,80, y=T,R, z=ES,DS,ESS,DSS) with serial number 17X**** or later, and versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5U-xMy/z (x=32,64,80, y=T,R, z=ES,DS,ESS,DSS) with serial number 179**** and prior, and versions 1.074 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-xMy/z (x=32,64,96, y=T, z=D,DSS)) with serial number 17X**** or later, and versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-xMy/z (x=32,64,96, y=T, z=D,DSS)) with serial number 179**** and prior, and versions 1.074 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-32MT/DS-TS versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-32MT/DSS-TS versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UJ-xMy/z (x=24,40,60, y=T,R, z=ES,ESS) versions 1.042 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UJ-xMy/ES-A (x=24,40,60, y=T,R) versions 1.043 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5S-xMy/z (x=30,40,60,80, y=T,R, z=ES,ESS) versions 1.003 and prior, Mitsubishi Electric Corporation MELSEC iQ-F Series FX5UC-32MR/DS-TS versions 1.280 and prior, Mitsubishi Electric Corporation MELSEC iQ-R Series R00/01/02CPU versions 33 and prior, Mitsubishi Electric Corporation MELSEC iQ-R Series R04/08/16/32/120(EN)CPU versions 66 and prior allows a remote unauthenticated attacker to access the Web server function by guessing the random numbers used for authentication from several used random numbers.

Affected products

• Mitsubishielectric Fx5S-30Mr/Es Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-30Mt/Es Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-30Mt/Ess Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-40Mr/Es Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-40Mt/Es Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-40Mt/Ess Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-60Mr/Es Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-60Mt/Es Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-60Mt/Ess Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-80Mr/Es Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-80Mt/Es Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5S-80Mt/Ess Firmware: before 1.003 — fixed in 1.003
• Mitsubishielectric Fx5U-32Mt/Dss Firmware: all versions
• Mitsubishielectric Fx5U-64Mt/Dss Firmware: all versions
• Mitsubishielectric Fx5U-80Mt/Dss Firmware: all versions
• Mitsubishielectric Fx5U-80Mt/Ess Firmware: all versions
• Mitsubishielectric Fx5Uc-32Mr/Ds-Ts Firmware: before 1.280 — fixed in 1.280
• Mitsubishielectric Fx5Uc-32Mt/D Firmware: all versions
• Mitsubishielectric Fx5Uc-32Mt/Ds-Ts Firmware: before 1.280 — fixed in 1.280
• Mitsubishielectric Fx5Uc-32Mt/Dss-Ts Firmware: before 1.280 — fixed in 1.280
• Mitsubishielectric Fx5Uc-32Mt/Dss Firmware: all versions
• Mitsubishielectric Fx5Uc-64Mt/D Firmware: all versions
• Mitsubishielectric Fx5Uc-64Mt/Dss Firmware: all versions
• Mitsubishielectric Fx5Uc-96Mt/D Firmware: all versions
• Mitsubishielectric Fx5Uc-96Mt/Dss Firmware: all versions
• Mitsubishielectric Fx5Uj-24Mr/Es-A Firmware: before 1.043 — fixed in 1.043
• Mitsubishielectric Fx5Uj-24Mr/Es Firmware: before 1.042 — fixed in 1.042
• Mitsubishielectric Fx5Uj-24Mt/Es-A Firmware: before 1.043 — fixed in 1.043
• Mitsubishielectric Fx5Uj-24Mt/Es Firmware: before 1.042 — fixed in 1.042
• Mitsubishielectric Fx5Uj-24Mt/Ess Firmware: before 1.042 — fixed in 1.042

How to fix

Upgrade to a fixed version: Mitsubishielectric Fx5S-30Mr/Es Firmware 1.003; Mitsubishielectric Fx5S-30Mt/Es Firmware 1.003; Mitsubishielectric Fx5S-30Mt/Ess Firmware 1.003; Mitsubishielectric Fx5S-40Mr/Es Firmware 1.003; Mitsubishielectric Fx5S-40Mt/Es Firmware 1.003; Mitsubishielectric Fx5S-40Mt/Ess Firmware 1.003; Mitsubishielectric Fx5S-60Mr/Es Firmware 1.003; Mitsubishielectric Fx5S-60Mt/Es Firmware 1.003; Mitsubishielectric Fx5S-60Mt/Ess Firmware 1.003; Mitsubishielectric Fx5S-80Mr/Es Firmware 1.003; Mitsubishielectric Fx5S-80Mt/Es Firmware 1.003; Mitsubishielectric Fx5S-80Mt/Ess Firmware 1.003. Check the vendor advisory for mitigations.

References

• https://jvn.jp/vu/JVNVU99673580/index.html
• https://www.cisa.gov/uscert/ics/advisories/icsa-23-017-02
• https://www.mitsubishielectric.com/en/psirt/vulnerability/pdf/2022-019_en.pdf
• https://jvn.jp/vu/JVNVU99673580/index.html
• https://www.cisa.gov/uscert/ics/advisories/icsa-23-017-02
• https://www.mitsubishielectric.com/en/psirt/vulnerability/pdf/2022-019_en.pdf
• https://www.talosintelligence.com/vulnerability_reports/TALOS-2022-1646

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