Integer-Underflow.md

[H-01] Integer Underflow in Balance Deduction

Severity: High Vulnerability Type: Math Error

Description

In Solana programs, standard subtraction - can lead to an integer underflow if the result is negative. Since Rust types like u64 are unsigned, a result of -1 becomes a massive positive number.

Vulnerable Code

user.balance -= amount; // No check if amount > balance


user.balance = user.balance.checked_sub(amount).ok_or(error::InsufficientFunds)?;