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Integer Overflow

What it detects​

The detector analyzes addition and multiplication that can overflow when executed inside unchecked blocks or on Solidity versions prior to 0.8. Overflowed values wrap to zero or a small number, breaking contract logic.

Typical symptoms​

  • Account balances or counters reset unexpectedly to small values (e.g., zero)
  • Arithmetic within unchecked blocks that assumes overflow won’t happen
  • Contracts using addition or multiplication in loops or without input constraints

Solidity snippet (v0.8.25)​

pragma solidity ^0.8.25;

contract Overflow {
    function add(uint256 a, uint256 b) external pure returns (uint256) {
        unchecked {
            // Wraps on overflow
            return a + b;
        }
    }
}

In the above code, if a and b are large enough to overflow uint256, the result will silently wrap around to a much smaller value, potentially causing logical or financial errors.

Why it matters on EVM​

Integer overflows in the EVM can allow:

  • Bypassing accounting checks
  • Draining or inflating balances
  • Skipping loop termination conditions
  • Creating denial-of-service or infinite loop scenarios

Even though Solidity 0.8+ includes built-in overflow protection, unsafe usage of unchecked can reintroduce this classic vulnerability.

Never use unchecked unless you're 100% sure overflow is impossible or irrelevant.