Is the Reentrancy Attack Still a Significant Problem?

What is a Reentrancy Attack?

Reentrancy is a type of attack that can occur in smart contracts that allow untrusted external code to be executed within the contract. This can happen when a smart contract calls an external contract, and the external contract then calls back into the original contract, potentially causing an infinite loop. A reentrancy attack is a method of exploiting a vulnerability in a smart contract that allows an attacker to repeatedly call a function in the contract, causing an infinite loop and potentially stealing funds....

Example of a Reentrancy Attack

The standard reentrancy attack is where an attacker repeatedly calls a function in a contract, causing an infinite loop and potentially stealing funds. A user interacts with the Vulnerable Smart Contract to deposit funds....

How Does Reentrancy Attack Work?

Below is an example to explain the working of a reentrancy attack:...

Types of Reentrancy Attack

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Reentrancy Smart Contract Attacks Examples

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Is the Reentrancy Attack Still a Significant Problem?

There are several types of reentrancy attacks, including:...

How to Protect Smart Contracts Against a Reentrancy Attack?

DAO Hack: The DAO (Decentralized Autonomous Organization) smart contract was a decentralized investment fund built on the Ethereum blockchain. An attacker discovered a vulnerability in the DAO smart contract that allowed them to repeatedly call the “split” function, which allowed investors to withdraw their funds from the DAO before the contract had a chance to update the internal balances. The attacker was able to use this vulnerability to repeatedly call the split function and drain the DAO of approximately $50 million worth of Ether (ETH). Lendf.me Protocol: Lendf.me is a decentralized lending platform built on the Ethereum blockchain. In 2019 an attacker discovered a vulnerability in the smart contract that allowed them to repeatedly borrow and repay the same loan over and over again, while also manipulating the price of the underlying assets to increase the amount of the loan. The attacker was able to exploit this vulnerability to borrow and repay a single loan multiple times, stealing more than $350,000 worth of cryptocurrency assets from the platform. Cream Finance: Cream Finance is a DeFi platform that allows users to lend and borrow assets. In 2020 an attacker discovered a vulnerability in the smart contract that allowed them to repeatedly borrow and repay the same loan over and over again, while also manipulating the price of the underlying assets to increase the amount of the loan. The attacker was able to exploit this vulnerability to borrow and repay a single loan multiple times, stealing more than $30 million worth of cryptocurrency assets from the platform. BurgerSwap: BurgerSwap is a decentralized exchange built on the Binance Smart Chain. In 2021 an attacker discovered a vulnerability in the smart contract that allowed them to repeatedly borrow and repay the same loan over and over again, while also manipulating the price of the underlying assets to increase the amount of the loan. The attacker was able to exploit this vulnerability to borrow and repay a single loan multiple times, stealing more than $2 million worth of cryptocurrency assets from the platform. SurgeBNB: SurgeBNB is a decentralized exchange built on the Binance Smart Chain. In 2021 an attacker discovered a vulnerability in the smart contract that allowed them to repeatedly borrow and repay the same loan over and over again, while also manipulating the price of the underlying assets to increase the amount of the loan. The attacker was able to exploit this vulnerability to borrow and repay a single loan multiple times, stealing more than $30 million worth of cryptocurrency assets from the platform. Siren Protocol: Siren Protocol is a decentralized finance platform built on the Ethereum blockchain. In 2021 an attacker discovered a vulnerability in the smart contract that allowed them to repeatedly borrow and repay the same loan over and over again, while also manipulating the price of the underlying assets to increase the amount of the loan. The attacker was able to exploit this vulnerability to borrow and repay a single loan multiple times, stealing more than $30 million worth of cryptocurrency assets from the platform....

Conclusion

Reentrancy attacks are still a significant problem in the smart contract ecosystem. Though many smart contract platforms and development frameworks have built-in protections against reentrancy, it still remains an ongoing threat to smart contract security. As new smart contracts and decentralized applications are developed, it’s important for developers to thoroughly test and audit their contracts to ensure they are protected against reentrancy attacks....