How a 10 ETH Refund Bug Froze THORChain Trading on 10 Chains

At 11:34 UTC on October 31, a one-block Ethereum reorganization removed a block containing a 10 ETH deposit to a THORChain vault that THORChain had credited. THORChain refunded 10 ETH, and the sender’s accepted-chain deposit was refunded too, so 20 ETH left the vault for one 10 ETH deposit; the sender later returned the extra 10 ETH. THORChain’s solvency checker halted ETH swaps, and node operators stopped ETH signing within two minutes, then halted trading on other chains because its warning that a reorg could allow reuse of the same transaction number applies to any connected chain. On November 1, THORChain reported ten chains halted and four active, with core developers working on changes and no reopening date.