Unicast Reverse Path Forwarding (uRPF) is the primary and the standard Source Address Validation (SAV) mechanism to combat IP spoofing and mitigate Denial-of-Service (DoS) and other attacks. However, in this study, we reveal a critical and previously unexplored vulnerability in uRPF that adversaries can stealthily exploit through Border Gateway Protocol (BGP) hijacking. We introduce Stealthy BGP Attack against uRPF (SBA-uRPF), a novel attack vector that leverages prefix hijacking to manipulate uRPF filtering decisions, resulting in the unintended blocking of legitimate traffic and the facilitation of persistent DoS attacks. Due to its hidden nature, SBA-uRPF attacks could pose a significant and persistent security risk.