The Standard

Summary

Re-entrancy is a vulnerability that can cause a contract to be attacked, leading to the loss of funds.

Vulnerability Details

ERC20 tokens generally do not result in re-entrancy, however ERC777 tokens can and they can masquerade as ERC20 tokens. It is better to be safe and consider that transfers can create re-entrancy problems.

Impact

In the last two years, although the reentrancy attack is considered to be quite old, there have been cases such as:

CREAM FINANCE hack (August 2021) ($18.8 million, reentrancy vulnerability allowed the exploiter for the second borrow.)

Siren protocol hack (September 2021) ($3.5 million, AMM pools were exploited through reentrancy attack.

Tools Used

Manual

Recommendations

Use Openzeppelin or Solmate Re-Entrancy pattern