Not Quite Water Under the Bridge
summary
Survey of cross-chain bridge failures shows concrete exploits and how they work: attackers use custodian vault admin takeover by replaying encoded calldata across chains to gain privileged access; unchecked proof-of-burn bytes create replayable proofs that allow multiple withdrawals; a plug-in verifier that accepts any signature lets attackers mint unlimited wrapped tokens; event-reading communicators are vulnerable to event oracle poisoning by submitting duplicate events; permit fallbacks that never revert let bridges drain approved ERC‑20s; a mining reorg could enable multi-million dollar double-spends.
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chapters (10)
- 0:00Introduction
- 1:24What is a bridge
- 2:15How do bridges work
- 6:09Attacking the custodian
- 8:03Crosschain function calls
- 10:37Proof of burn
- 13:35Communicator
- 14:28Ethereum Read Events
- 15:51Revoking Approvals
- 17:06Potential Big Picture Attacks
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