The underlying mechanics of this Binance attack
The attack’s point of entry was EIP-7702, introduced with Ethereum’s Pectra upgrade.
Put simply, EIP-7702 allows a regular EOA wallet to temporarily delegate the execution of a piece of contract code. Once authorization is signed, that wallet address gains smart contract capabilities.
The attacker had obtained 50 sets of EIP-7702 authorizations signed by Binance’s hot wallet in advance, each with a different nonce.
Since he couldn’t know the wallet’s exact current nonce ahead of time, he broadcast all 50 authorizations at once. If even one had a nonce matching the wallet’s current state, the delegation would take effect.
That single matching authorization was enough to bind a sweeping contract to Binance’s hot wallet address, allowing the hacker to drain all the assets in the wallet in an instant.
Here’s the key point: the TRX stablecoin transfer on the Tron chain wasn’t made by the hacker. Binance made it as part of an internal funds transfer between exchange wallets, so don’t include it in the stolen-funds tally.
Many people saw only the 5.6 billion flowing out, but missed what makes this vulnerability so terrifying.
It wasn’t a direct leak of the private key; the signature authorization mechanism was exploited. Once the nonce matched, the contract took over the account and drained it in one go.
EIP-7702 was originally meant to pave the way for account abstraction. Now it has become a weapon for draining massive hot wallets.
The attack’s point of entry was EIP-7702, introduced with Ethereum’s Pectra upgrade.
Put simply, EIP-7702 allows a regular EOA wallet to temporarily delegate the execution of a piece of contract code. Once authorization is signed, that wallet address gains smart contract capabilities.
The attacker had obtained 50 sets of EIP-7702 authorizations signed by Binance’s hot wallet in advance, each with a different nonce.
Since he couldn’t know the wallet’s exact current nonce ahead of time, he broadcast all 50 authorizations at once. If even one had a nonce matching the wallet’s current state, the delegation would take effect.
That single matching authorization was enough to bind a sweeping contract to Binance’s hot wallet address, allowing the hacker to drain all the assets in the wallet in an instant.
Here’s the key point: the TRX stablecoin transfer on the Tron chain wasn’t made by the hacker. Binance made it as part of an internal funds transfer between exchange wallets, so don’t include it in the stolen-funds tally.
Many people saw only the 5.6 billion flowing out, but missed what makes this vulnerability so terrifying.
It wasn’t a direct leak of the private key; the signature authorization mechanism was exploited. Once the nonce matched, the contract took over the account and drained it in one go.
EIP-7702 was originally meant to pave the way for account abstraction. Now it has become a weapon for draining massive hot wallets.