The Attack: Root Cause and Mechanics
Published 7/18/2026, 12:18:30 AM
Across Protocol's Solana bridge was exploited on July 17, 2026, resulting in a loss of capital for the protocol's primary relayer, Risk Labs, while user funds remained entirely safe [Source: https://x.com/AcrossProtocol/status/2078036118209982566]. The incident highlights the security advantages of Across's "intent-based" architecture, where relayers assume the financial risk of bridge operations rather than users.
The Attack: Root Cause and Mechanics
The exploit targeted the Risk Labs relayer, the off-chain infrastructure responsible for fulfilling user bridge requests. The vulnerability resided in the off-chain event handling between Solana's on-chain state and the relayer software [Source: https://phemex.com/news/across-protocol-solana-exploit-mechanics].
- Event Spoofing: Attackers likely exploited a "trust boundary" seam where the relayer monitors Solana for user deposits. On Solana, failed transactions can still emit data that off-chain systems might misinterpret. The attacker spoofed deposit events, tricking the relayer into "filling" orders (paying out funds on a destination chain like Ethereum) for deposits that never actually occurred [Source: https://blog.asymmetric.re/across-solana-event-spoofing/].
- Scope: The attack was limited to the Solana-to-Ethereum and Solana-to-Base pathways. Other chains remained operational as they utilize different relayer logic or instances [Source: https://cryptobriefing.com/across-solana-incident-report].
Why User Funds Remained Safe
The primary reason user funds were unaffected is Across's Intent-Based Design, which fundamentally differs from traditional "Lock-and-Mint" bridges.
| Feature | Traditional Bridges (e.g., Wormhole, Ronin) | Across Protocol |
|---|---|---|
| Asset Custody | Users deposit into a central, pooled vault. | Users do not hand custody to a shared pool. |
| Risk Bearer | Users lose funds if the central vault is drained. | Relayers lose their own capital if exploited. |
| Settlement | Relies on multi-sigs or validator sets. | Relies on the UMA Optimistic Oracle for verification. |
| Incident Outcome | Historically hundreds of millions lost. | $0 user funds lost in the Solana incident. |
In the Across model, a relayer uses its own private capital to fulfill a user's intent immediately. The relayer is only reimbursed by the protocol after the transaction is verified. Because the exploit occurred during this fulfillment phase, the attacker drained the relayer's liquidity, not the users' deposits [Source: https://cryptobriefing.com/across-solana-incident-report].
Current Status and Impact
Following the incident, Across temporarily disabled Solana deposits to conduct a full security review. All in-flight user transactions were completed successfully, and the protocol continues to process refunds for any stuck transactions automatically [Source: https://x.com/AcrossProtocol/status/2078036118209982566]. While the exact capital loss to Risk Labs has not been publicly specified, the protocol's core security model prevented a wider contagion that typically follows bridge hacks [Source: https://kucoin.com/news/across-protocol-security-milestones].
Specific technical details regarding the exact implementation flaw in the relayer code remain undisclosed as of the latest incident reports.