PhantomRPC is an architectural weakness in the Windows Remote Procedure Call (RPC) runtime that allows low-privileged processes to escalate to SYSTEM or Administrator by impersonating privileged clients. Disclosed by Kaspersky’s Haidar Kabibo at Black Hat Asia 2026, the flaw stems from how rpcrt4.dll handles connections to unavailable RPC servers: when a privileged process attempts an RPC call to a server