Unchecked External Calls

Description

In Ethereum, when a contract calls another contract, the called contract can fail silently without throwing an exception. If the calling contract doesn’t check the outcome of the call, it might assume that the call was successful, even if it wasn’t.

Impact

Unchecked external calls can lead to failed transactions, lost funds, or incorrect contract state.

Steps to Fix

1. Always check the return value of call, delegatecall, and callcode.
2. Use Solidity’s transfer or send functions instead of call.value()(), as they automatically reverts on failure.

Example

A contract uses the call function to send Ether to an address. If the call fails (for example, if the recipient is a contract without a payable fallback function), the sending contract might incorrectly assume the transfer was successful.