Summer.fi Lazy Summer attack is not a contract vulnerability, but rather an exploitation of the NAV mechanism

Summer.fi released an analysis report on the Lazy Summer Protocol USDC treasury attack incident. The attacker manipulated the prices of two USDC treasury shares in a single atomic transaction, extracting approximately $6.04 million of depositor funds. The core of the attack lies in the calculation method of the treasury's net asset value (NAV).

The attacker donated tokens that still retained the old valuation to a Silo Ark that had been suspended after the incident in November 2025 but had not yet been completely removed, resulting in an inflated total asset value of approximately 9.5%, raising the share price, which was then redeemed at an inflated price and withdrawn from the treasury's actual liquidity. The report emphasizes that this attack was not due to a contract code vulnerability, but rather a missing link in the treasury's offline process—the deposit limit for that Ark had been set to zero, yet it was still counted in the NAV of active assets.

The attacker premeditatedly accumulated the required tokens three months in advance through multiple wallets and transferred part of the profits via Tornado Cash. After the incident, Guardian Multisig has suspended all on-chain treasuries and set the deposit limit to zero. The Lazy Summer DAO will discuss compensation plans for affected users and the treasury restart plan in the coming days.