$50 Million DeFi Swap Loss Triggers Post Mortems From Aave and CoW Swap

A major decentralized finance trading incident on March 12 has prompted separate post mortem reports from Aave and CoW Swap after a user exchanged more than $50.4 million worth of aEthUSDT for approximately $36,000 in aEthAAVE through the swap widget integrated on Aave’s interface. The transaction is widely viewed as one of the largest execution losses recorded in decentralized finance markets.

Both teams confirmed the core details of the trade but emphasized different causes. Aave attributed the loss primarily to extreme price impact in a highly illiquid market, while CoW Swap pointed to multiple infrastructure failures that worsened the execution outcome.

Illiquid Market Conditions and User Confirmation

According to Aave’s report, the swap route involved redeeming aEthUSDT for USDT on Aave V3, converting USDT to WETH through a Uniswap V3 pool, and finally trading WETH for AAVE in a SushiSwap pool with roughly $73,000 in liquidity. The interface displayed a warning indicating a potential 99.9% price impact and required manual confirmation before execution.

Following the incident, Aave introduced “Aave Shield,” a safeguard designed to block swaps with price impact exceeding 25% unless users manually disable the protection.

Infrastructure Failures Identified by CoW Swap

CoW Swap described a series of technical issues that contributed to the outcome. The platform’s quote verification system rejected better-priced routes because of a hardcoded gas ceiling of 12 million units. As a result, the only verified quote offered roughly 329 AAVE, far below alternative estimates that could have returned between $5 million and $6 million in tokens.

During the auction process, another solver identified a better route and won two bids but never submitted the transactions onchain. After those attempts failed, weaker bids remained, leaving the order to execute at a severely degraded price.

Mempool Leak and MEV Profits

Investigators also observed signs that the transaction may have leaked from a private mempool, allowing backrunning activity. Blockchain analytics data indicates that a block builder extracted about $34 million in ETH during the transaction block, while a separate MEV bot gained roughly $9.9 million through a sandwich trade.

The user involved in the swap has not contacted either protocol team, and the funds are currently being held.

Governance Questions and Revised Fee Figures

The event also highlighted governance tensions surrounding swap fees tied to the integration. Aave clarified that the actual fee from the transaction was $110,368 based on a 25-basis-point charge, revising an earlier estimate of about $600,000.

Debate over where these swap fees are directed within the protocol’s ecosystem continues, adding further scrutiny to governance and operational practices across decentralized finance platforms.

Disclaimer

This content is for informational purposes only and does not constitute financial, investment, or legal advice. Cryptocurrency trading involves risk and may result in financial loss.