Eleven Finance - REKT


This one almost struck a nerve.

Eleven.finance, a yield aggregator on Binance Smart Chain (BSC) and Polygon (MATIC) was exploited for a total of $4.5M.

Some feared that it was the much larger Nerve Finance who was under attack, but it was in fact the NRV vault of Eleven Finance.

There’s no rest for the wicked - who would attack at such an ungodly hour?

Credit: 0xdeadf4ce

Transaction details here.

The root cause was a function called emergencyBurn() in the intermediary vault used to track anySwap / Nerve-bridged assets nrvBTC, nrvETH and nrvFUSDT in the Eleven “MasterMind” farming contract.

The attacker first took a Flashloan of each asset’s underlying token balance in the “MasterMind” contract (Binance-pegged BTC, ETH and USDT) to convert these into nrvBTC, nrvETH and nrvFUSDT respectively.

Nerve 3Pool and PancakeSwap BUSD - NRV liquidity provider positions were also affected.

A vulnerable function emergencyBurn() in the intermediate vault contract allowed the attacker to withdraw the deposited balance without having the withdrawal being accounted for internally.

As a result the attacker was able to not only remove his own deposit but the full balance of the same amount that had been in the vault before as well.

The attacker used the Nerve bridge to transfer out 2,293 ETH in proceeds to the address 0xdb2d590aCe7cAe51DF1fB3312738038Ec032Bf33.

Steps

1: borrow underlying assets from PancakeSwap (Flash Swap)

2: convert amount (mint) to Nerve asset

3: deposit Nerve asset to “MasterMind” through intermediate vault

4: call emergencyBurn() on intermediate vault, transferring an amount equal to the previously deposited amount (equal to vault balance before attack) to the attacker

5: proceed with a regular withdrawal, transferring the previously deposited asset balance back to the attacker

Funds lost

30.75 BTCB for ~$1.05M from nrvBTC

286 ETH for ~$561K from nrvETH

2.241M BUSD for ~$2.241M from NRV 3Pool LP

0.647M BUSD for $647K from NRV - BUSD LP

$4.5 million gone, entering at position 27 on the ever expanding rekt leaderboard.

Peckshield blamed this on a “dumb logic issue”; a shockingly simple way to lose over four million dollars.

Fear and greed is on the rise, will we see more attacks now that honest work is harder to find?

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