THORChain Pauses Swaps on 10 Chains After Reorg Triggers Refund Bug
Node operators halted cross-chain swaps after an Ethereum block reorg exposed a refund flaw that paid out 10 ETH the vaults never received.
Key Takeaways
- THORChain paused swaps on 10 networks on October 31 after an Ethereum block reorg exposed a refund bug in its vaults.
- The vaults paid an extra 10 ETH refund for a deposit that never confirmed, and the recipient returned it.
- Avalanche, Base and XRP still trade. Node operators will re-enable other chains one by one once each is confirmed safe.
THORChain (RUNE) halted cross-chain swaps on 10 networks on October 31 after a one-block Ethereum reorganization exposed a refund bug in its vaults. Node operators paused Bitcoin, Ethereum, Solana, Tron and six other chains. Avalanche, Base and XRP kept trading.
How The Refund Bug Works
The incident began at 11:34 UTC on October 31. A one-block Ethereum reorg removed a 10 ETH deposit that THORChain had already credited. When the swap failed its price limit, the protocol issued a refund against funds the vault had never actually received on the canonical chain. The sender's real deposit was refunded as well, producing an extra 10 ETH payout.
An automatic solvency checker caught the shortfall and paused ETH swaps. Node operators stopped ETH outbound signing within about two minutes, then used emergency three-node votes to pause chains one by one while developers investigated. The recipient returned the extra 10 ETH and the project says solvency is restored.
The flaw is a timing problem. Reorg detection and re-checks let the bad state finalize before the network noticed. THORChain warned that anyone could now repeat the pattern. "Now that this is public knowledge, every time there is a block re-org on an external chain, a malicious actor could perform a new transaction with the same nonce and would be paid funds by the THORChain vaults," the project said in a status update on X.
Which Chains Are Paused
Swaps are paused on 10 networks: Cosmos, Bitcoin Cash, BNB Chain, Bitcoin, Dogecoin, Ethereum, Litecoin, Solana, Tron and Zcash. Avalanche, Base and XRP remain open, according to the protocol's network status page. THORChain is a cross-chain swap network and one of the established DEX tokens among DeFi coins on Coinranking.
The pause covers swaps that touch the affected chains. Liquidity providers and traders on the three open networks are unaffected. The project's THORChain (RUNE) token trades on every open chain, and the THORChain price chart shows it down about 21% over the 24 hours to November 2.
What Happens Next
Core developers are implementing fixes for the refund logic. Node operators will vote to re-enable chains one by one once each is confirmed safe, the project said. No date is set. Beyond the temporary overpayment, which was returned, THORChain has not reported user losses from the incident.
Frequently Asked Questions
Why Did THORChain Pause Swaps?
An Ethereum block reorg exposed a refund bug that let the vaults pay out a 10 ETH refund for a deposit they never received. Node operators paused swaps while developers fix the flaw.
Were Any Funds Lost in the THORChain Incident?
No. The recipient returned the extra 10 ETH and the project says its vaults are solvent again.
Which Chains Are Still Trading on THORChain?
Avalanche, Base and XRP remain open. Ten networks, including Bitcoin, Ethereum, Solana and Tron, are paused.
When Will THORChain Swaps Resume?
No date is set. Node operators will re-enable chains one by one once each is confirmed safe.
Sources
- THORChain status update on the swap halt and refund bug · THORChain
- THORChain halts swaps after block reorg bug · Cointelegraph
Prices and market data: Coinranking.
