What happened
On May 20, 2026, RetoSwap lost an estimated $2.7 million (about 7,000 XMR) when an attacker abused a Haveno trade-protocol authentication flaw. A forged ACK message redirected the arbitrator role during multisig-wallet setup to an attacker-controlled address.
How it happened
- The attacker joined a trade as a buyer or seller, obtaining one key in its 2-of-3 multisig flow.
- Before the multisig wallet was created, the attacker sent a forged, out-of-order ACK message that carried an attacker-controlled
.onionaddress and impersonated the arbitrator. - The client accepted that address without cryptographically checking it against the expected arbitrator public key.
- Multisig setup was then routed to the attacker, who acquired the arbitrator's signing position.
- After counterparties deposited funds into the compromised wallet, the attacker could move the balance.
Protocol details
Evidence
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