Cross-Contract Reentrancy

Cross-contract reentrancy is a sophisticated attack vector where an attacker exploits a vulnerability in one contract to trigger a malicious state change in a different, related contract. This often happens when contracts share a dependency or interact within the same transaction flow, and one contract fails to properly secure its external calls.

By nesting calls across multiple contracts, the attacker can bypass standard reentrancy guards that only check the state of the local contract. Preventing this requires a holistic security approach, where all interacting contracts must be designed with consistent security patterns and minimal trust assumptions.

This threat highlights the importance of auditing the entire ecosystem of a protocol, rather than just individual contracts. It is a critical concern for composable DeFi applications where multiple protocols interact.