Ophir leads the security research team in Akamai's Enterprise Security Group. Peleg is a security researcher. Executive summary \r\n \r\n Guardicore Labs, in collaboration with SafeBreach Labs, found a  critical vulnerability in Hyper-V’s virtual network switch driver ( vmswitch.sys ). \r\n The vulnerability was found using an in-house built fuzzer we named  hAFL1 and which we  open-source  today . The repository includes detailed, step-by-step instructions on how to deploy and run the fuzzer on a Linux server. \r\n hAFL1 is a modified version of  kAFL  which enables fuzzing Hyper-V paravirtualized devices and adds structure awareness, detailed crash monitoring and coverage guidance. \r\n The RCE vulnerability we found ( CVE-2021-28476 ) was assigned a CVSS score of 9.9 and is detailed in a separate blog post.…