IPv4 addresses have become a commodity with monetary value since the exhaustion of unallocated IPv4 space. This led to the rise of a secondary market for buying, selling, and leasing IPv4 addresses. While prior work has studied the IPv4 transfer behavior, the IPv4 leasing ecosystem remains largely unexplored. In this paper, we analyze the IPv4 leasing ecosystem by designing a methodology to infer leased address space for all RIRs and study its impact on routing and hosting security. We infer that 4.1% of all advertised IPv4 prefixes (0.9% of routed v4 address space) were leased in April 2024. Our method achieves 98% precision when evaluated against our validated dataset. Finally, we show that leased address space is five times more likely to be abused compared to non-leased space.