Improper Input Validation vulnerability in MELSEC iQ-R Series R00/01/02CPU Firmware versions "24" and prior, MELSEC iQ-R Series R04/08/16/32/120(EN)CPU Firmware versions "57" and prior, MELSEC iQ-R Series R08/16/32/120SFCPU All versions, MELSEC iQ-R Series R08/16/32/120PCPU Firmware versions "29" and prior, MELSEC iQ-R Series R08/16/32/120PSFCPU All versions, MELSEC iQ-R Series R16/32/64MTCPU All versions, MELSEC iQ-R Series R12CCPU-V All versions, MELSEC Q Series Q03UDECPU All versions, MELSEC Q Series Q04/06/10/13/20/26/50/100UDEHCPU All versions, MELSEC Q Series Q03/04/06/13/26UDVCPU The first 5 digits of serial No. "23071" and prior, MELSEC Q Series Q04/06/13/26UDPVCPU The first 5 digits of serial No. "23071" and prior, MELSEC Q Series Q12DCCPU-V All versions, MELSEC Q Series Q24DHCCPU-V(G) All versions, MELSEC Q Series Q24/26DHCCPU-LS All versions, MELSEC Q Series MR-MQ100 All versions, MELSEC Q Series Q172/173DCPU-S1 All versions, MELSEC Q Series Q172/172DSCPU All versions, MELSEC Q Series Q170MCPU All versions, MELSEC Q Series Q170MSCPU(-S1) All versions, MELSEC L Series L02/06/26CPU(-P) All versions, MELSEC L Series L26CPU-(P)BT All versions and MELIPC Series MI5122-VW All versions allows a remote unauthenticated attacker to cause a denial-of-service (DoS) condition by sending specially crafted packets. System reset is required for recovery.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-20611
• https://jvn.jp/vu/JVNVU94434051/index.html
• https://us-cert.cisa.gov/ics/advisories/icsa-21-334-02
• https://www.mitsubishielectric.com/en/psirt/vulnerability/pdf/2021-019_en.pdf