Three Sui Exploits, One Root Cause: Why 'The Math Looked Fine' Keeps Costing $224M+

Three Sui Exploits, One Disease — Why ‘The Math Looked Fine’ Keeps Costing Hundreds of Millions

A single missing comparison cost Cetus $223M, Aftermath $1.14M, and Bucket Protocol remains vulnerable. All three passed audits by top firms.

Why This Matters

Three Sui protocols – Cetus, Aftermath, and Bucket – lost or risk losing over $224 million to arithmetic bugs that all passed audits. The ideal of safe smart contracts breaks on a single missing comparison, because Move’s compile-time guarantees stop at integer overflow. The real cost of invisible boundary errors is nine figures, and the fix is always one line.

Key Insights

• Cetus lost $223M in May 2025 due to a shift overflow in checked_shlw – the assert was off by one bit (source: Cyfrin).
• Aftermath lost $1.14M in April 2026 from a negative fee – only upper bound validated, signed comparison passed (source: DarkNavy).
• Bucket Protocol’s debt health functions can overflow when collateral decimals exceed BUCK decimals – found July 2026, unpatched (source: OtterSec audit).
• Auditors miss arithmetic bugs because the check looks complete – rational under time pressure; static analysis catches them in milliseconds.
• Move’s safety guarantees prevent reentrancy and type errors but not integer overflow – the gap is at the math layer.

Working Examples

Cetus’s checked_shlw function – the assert passes incorrectly for inputs near 2^192, causing a shift overflow.

// BEFORE fix
assert!(n <= MAX_U256 >> 64, ERR_OVERFLOW);
n << 64

Aftermath’s fee validation – only upper bound checked, allowing negative fees to pass.

assert!(integrator_taker_fee <= max_taker_fee, E_INVALID);

Bucket Protocol’s compute_collateral_value_to_buck – u64 multiplication after safe u128 promotion, risking overflow.

let collateral_raw_value = mul_factor(collateral_amount, price, denominator);
collateral_raw_value * pow(10, constants::buck_decimal() - collateral_decimal)

Practical Applications

• Use case: Cetus uses checked_shlw in liquidity delta calculation – pitfall: relying on a library function whose assert is mathematically incomplete.
• Use case: Aftermath allows third-party fee setting – pitfall: only upper bound check, enabling negative fees that inflate collateral.
• Use case: Bucket Protocol’s create_bucket adds new collateral with arbitrary decimals – pitfall: no overflow guard in compute_collateral_value_to_buck, safe only by accident today.

References:

• https://dev.to/mehvetero/three-sui-exploits-one-disease-why-the-math-looked-fine-keeps-costing-hundreds-of-millions-17f3