Aquifer allowed the caller to supply the input-side token program used during swaps instead of pinning it to the canonical SPL Token Program. The attacker supplied a malicious program that accepted Aquifer’s CPI transfer instruction and returned success without transferring the required input tokens. Aquifer failed to verify the actual input-token balance increase and consequently released real output tokens from its vaults without receiving payment

Solana-based proprietary AMM Aquifer was exploited for about $2.5 million. Public reporting points to compromised protocol-linked wallets or admin credentials rather than a confirmed smart-contract bug. The attacker operated addresses on both Solana and Ethereum. The same day, Aquifer’s Solana upgrade authority posted an on-chain white-hat offer: return at least 80% of stolen assets by September 3, 2026, 14:00 UTC to designated recovery addresses, and keep up to 20% as a bounty, in exchange for no civil claims by the project.