Across Protocol relayer loses $4M in Solana deposit spoof attack

A Risk Labs-operated relayer for Across Protocol lost under $4 million after an attacker fabricated $41.7 million in Solana deposit events, the cross-chain protocol said.

"The attacker exploited a gap in how our relayer validated Solana deposit events, causing it to pay out against fabricated proofs," the Across Protocol team said in a post-incident report.

The attacker created fake deposit events on Solana totaling $41.7 million, tricking the Risk Labs relayer into honoring roughly $4 million in corresponding payouts before the exploit was detected. Across Protocol paused its relayer operations on Solana after identifying the suspicious activity, the team said.

The incident adds to a brutal stretch for cross-chain infrastructure on Solana, where Allbridge lost $1.65 million in a flash loan attack earlier this month and BONK suffered a $20 million governance exploit. Across Protocol said it is working with security firms to trace the stolen funds and assess whether any user funds were directly affected.

Across Protocol lets users move assets between blockchains including Ethereum, Arbitrum, and Solana without minting wrapped tokens, relying instead on a network of relayers that front funds in exchange for fees. The Risk Labs-operated relayer was one of several third-party relayers supporting the protocol's Solana route.

The exploit follows a pattern of attacks targeting bridge infrastructure this year. More than $840 million has been lost to DeFi hacks in the first five months of 2026, with cross-chain systems accounting for some of the largest single losses. AFX Trade, a decentralized perpetuals exchange on Arbitrum, lost $24.15 million in a bridge exploit earlier this week.

This article is for informational purposes only and does not constitute investment advice.