CVE-2021-20611

CVE-2021-20611 is an Improper Input Validation vulnerability affecting numerous Mitsubishi Electric MELSEC iQ-R, Q, and L Series CPUs, as well as MELIPC Series MI5122-VW. A remote, unauthenticated attacker can exploit this by sending specially crafted packets, leading to a denial-of-service (DoS) condition that requires a system reset for recovery. Rated with a CVSS score of 7.5 (HIGH), this vulnerability is easily exploitable over the network with low attack complexity and no user interaction required, resulting in a complete loss of availability. The EPSS score is low, indicating a low probability of exploitation in the wild. Currently, there is no evidence of active exploitation, nor are there publicly available exploit modules in Metasploit, Nuclei, or ExploitDB. The vulnerability has received minimal community discussion and media coverage.