Across Protocol Relayer Suffers $4 Million Loss in Solana Exploit

The attack unfolded over 67 minutes on July 17, as an unknown actor utilized 1,627 single-use wallets to submit fake deposits across 18 chains. Risk Labs’ relayer processed 581 of these requests, resulting in a $4.5 million payout before the system was successfully halted. Because the attacker's own funds remained trapped within the protocol, the final financial impact was reduced to just under $4 million.

Risk Labs identified a software bug within its off-chain event-reading mechanism as the root cause, confirming that the protocol’s on-chain smart contracts and the Solana network itself remained secure. By suspending Solana operations before the remaining 1,046 fraudulent requests could be filled, the team invalidated approximately $37 million in potential additional losses.

Since the incident, Across has migrated its Solana routing to Circle’s Cross-Chain Transfer Protocol (CCTP) to prevent further vulnerabilities. The protocol affirmed that all legitimate user transfers were either completed or refunded on the day of the breach, and the incident will not impact the planned ACX token buyback program. At the time of reporting, the ACX token was trading at $0.041, reflecting a minor decline following the disclosure.