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title [Module 1](./BLOCKCHAIN_FUNDAMENTALS.md)6 — Master Smart Contract Audit Checklist
description Complete master audit checklist for smart contract security: pre-audit setup, per-function review (access control, input validation, CEI pattern, external calls, math), token handling (weird ERC-20, fee-on-transfer, rebasing), oracle validation, proxy and upgradeable contract review, DeFi-specific checklists (AMM, lending, vault/ERC-4626, governance, bridge), signature/cryptography, gas/DoS, MEV, economic security, and final pre-submission verification.
keywords smart contract audit checklist, security review checklist, ERC-4626 checklist, oracle validation checklist, proxy audit checklist, CEI pattern, audit methodology, DeFi security checklist, token handling audit, MEV checklist, economic security checklist, gas limit bypass, signature cryptography checklist
author Web3 Security Research
date 2025-01-01
last_modified_at 2026-03-21
og_title [Module 1](./BLOCKCHAIN_FUNDAMENTALS.md)6 — Master Audit Checklist | Web3 Hacker Guide
og_description Complete smart contract audit checklist: access control, CEI pattern, oracle validation, token quirks, proxy review, DeFi-specific checks, MEV, economic security, and pre-submission verification.
og_type article
twitter_card summary_large_image
canonical_url https://sdxshadow.github.io/Hack_web3/16_AUDIT_CHECKLIST_MASTER
schema_type TechArticle
difficulty All Levels
module 16
tags
audit-checklist
security-review
CEI-pattern
oracle-check
proxy-audit
token-handling
ERC-4626
DeFi-checklist
nav_order 16
parent Web3 Hacker & Pentester Guide

Module 16 — Master Audit Checklist

Difficulty: All Levels

This is your go-to reference during every audit. Print it, bookmark it, run through it systematically. Missing a single item on this list has cost auditors millions in missed findings.

16.1 Pre-Audit Setup Checklist

  • Clone repository and verify commit hash matches scope
  • Run: forge build (confirm no compilation errors)
  • Run: cloc contracts/src/ (understand codebase size)
  • Run: slither . (automated first pass)
  • Run: aderyn . (second automated pass)
  • Run: forge coverage (understand test coverage)
  • Read ALL documentation (README, docs/, whitepaper)
  • Read ALL previous audit reports
  • Run: git log --oneline -50 (recent changes)
  • Run: git diff AUDITED_COMMIT..HEAD (changes since last audit)
  • Map all contracts and their relationships
  • Identify all external dependencies (oracles, DEXes, bridges)
  • Identify all privileged roles (owner, admin, guardian, etc.)

16.2 Per-Function Checklist

Run this for EVERY external and public function:

Access Control

  • Is there appropriate access control?
  • Does it use msg.sender (not tx.origin)?
  • Are role checks correct (right role for the action)?
  • Can the access control be bypassed via delegatecall?
  • Is there a two-step ownership transfer (not instant)?
  • Are there any unprotected initializer functions?

Input Validation

  • Are all inputs validated?
  • What happens with amount = 0?
  • What happens with amount = type(uint256).max?
  • What happens with address = address(0)?
  • What happens with address = address(this)?
  • Are array lengths validated (matching lengths, max length)?
  • Are deadlines validated (not expired, not too far future)?

State Updates (CEI Pattern)

  • Are all state updates done BEFORE external calls?
  • Is there a reentrancy guard where needed?
  • Can the function be called recursively?
  • Can the function be called from a callback?
  • Is there cross-function reentrancy risk?
  • Is there read-only reentrancy risk (view functions called by others)?

External Calls

  • Is the return value of every external call checked?
  • Is SafeERC20 used for token transfers?
  • Is there a gas limit on external calls?
  • Can the external call reenter?
  • What happens if the external call reverts?
  • What happens if the external call returns unexpected data?
  • Is the called address trusted? Can it be changed?

Math

  • Is multiplication done before division?
  • Are there any division-by-zero possibilities?
  • Can any value overflow (even in Solidity 0.8+ with unchecked)?
  • Is rounding direction correct (round against user for safety)?
  • Are there precision loss issues with small amounts?
  • Are there precision loss issues with large amounts?
  • Is the math correct for edge cases (first/last depositor)?

16.3 Token Handling Checklist

  • Does the protocol handle fee-on-transfer tokens?
  • → Measure balance before/after transfer, not trust the amount
  • Does the protocol handle rebasing tokens?
  • → Use shares, not absolute balances
  • Does the protocol handle ERC-777 tokens?
  • → Reentrancy via tokensReceived hook
  • Does the protocol handle tokens with non-standard decimals?
  • → USDC = 6, WBTC = 8, not 18
  • Does the protocol handle tokens that return false instead of reverting?
  • → Use SafeERC20
  • Does the protocol handle pausable tokens?
  • → What happens if USDC is paused?
  • Does the protocol handle blacklistable tokens?
  • → What if the contract address is blacklisted?
  • Does the protocol handle tokens with multiple entry points?
  • → TUSD has two addresses
  • Does the protocol handle tokens with approval race conditions?
  • → USDT requires setting to 0 before changing allowance
  • Does the protocol handle tokens with no return value?
  • → USDT on mainnet

16.4 Oracle Checklist

  • What oracle(s) does the protocol use?
  • Is the price validated for staleness?
  • → require(block.timestamp - updatedAt <= heartbeat)
  • Is the price validated for completeness?
  • → require(updatedAt != 0)
  • Is the price validated for positivity?
  • → require(answer > 0)
  • Is the answeredInRound checked?
  • → require(answeredInRound >= roundId)
  • Is the L2 sequencer uptime checked? (for Arbitrum, Optimism, etc.)
  • Does the feed have minAnswer/maxAnswer circuit breakers?
  • → If so, what happens when real price is outside bounds?
  • Is a TWAP used instead of spot price?
  • → What is the TWAP window? Is it long enough?
  • Can the oracle be manipulated via flash loan?
  • What happens if the oracle returns 0?
  • What happens if the oracle returns max uint?
  • Is there a fallback oracle if the primary fails?

16.5 Proxy & Upgradeable Contract Checklist

  • What proxy pattern is used? (Transparent, UUPS, Beacon, Diamond)
  • Are EIP-1967 storage slots used for proxy variables?
  • Is there a storage collision between proxy and implementation?
  • Is the implementation initialized? (not just the proxy)
  • Is _disableInitializers() called in the implementation constructor?
  • Is there a timelock on upgrades?
  • Who can trigger upgrades? (multisig? timelock? single EOA?)
  • Is the upgrade function protected against reentrancy?
  • For UUPS: Is the upgrade function in the implementation (not proxy)?
  • For Diamond: Are facet selectors correctly mapped?
  • For Diamond: Can selectors clash between facets?
  • What is the storage layout? Does it match across versions?
  • Are __gap variables used for future storage slots?

16.6 DeFi-Specific Checklist

AMM / DEX

  • Is slippage protection enforced?
  • Is there a deadline parameter?
  • Is the price oracle manipulation-resistant?
  • Can the pool be drained via flash swap?
  • Are fee calculations correct?
  • Can liquidity be added/removed atomically to manipulate price?

Lending Protocol

  • Is collateral value calculated using a manipulation-resistant oracle?
  • Are borrow caps enforced?
  • Is the liquidation threshold correct?
  • Is the liquidation bonus reasonable (not too high)?
  • Can a user self-liquidate for profit?
  • Can bad debt be created?
  • Is there a minimum position size?
  • What happens during a market crash (cascading liquidations)?
  • Is interest accrual correct?
  • Can interest overflow?

Vault / ERC-4626

  • Is the first depositor protected against inflation attack?
  • → Virtual shares/assets offset, or minimum deposit
  • Is rounding direction correct?
  • → Deposits: round down (user gets fewer shares)
  • → Withdrawals: round up (user pays more assets)
  • Can the share price be manipulated via donation?
  • Is there a withdrawal fee or vesting period?
  • Can the vault be sandwiched (deposit before harvest, withdraw after)?
  • Is the totalAssets() calculation correct?
  • What happens if the underlying strategy loses funds?

Governance

  • Is voting based on snapshots (not current balance)?
  • Is there a timelock between proposal and execution?
  • Is the proposal threshold high enough to prevent spam?
  • Can a flash loan acquire enough voting power?
  • Are emergency functions protected by multisig?
  • Can proposals be executed before the voting period ends?
  • Is there a quorum requirement?
  • Can the governance contract be upgraded via governance?
  • → Circular dependency risk

Bridge

  • How are cross-chain messages verified?
  • Is there replay protection (nonce, message hash)?
  • Is the chain ID included in message verification?
  • Is the destination contract address included?
  • What is the validator/relayer trust model?
  • What happens if a message is never delivered?
  • What happens if the destination chain runs out of gas?
  • Is there a timeout/expiry mechanism?
  • Can the same message be processed twice?
  • Is the bridge contract upgradeable? Who controls upgrades?

16.7 Signature & Cryptography Checklist

  • Is EIP-712 used for typed data signing?
  • Does the domain separator include chainId?
  • Does the domain separator include verifyingContract?
  • Is there a nonce to prevent replay?
  • Is there a deadline to prevent stale signatures?
  • Is ECDSA.recover() used (not raw ecrecover)?
  • → OpenZeppelin's version enforces lower-s (prevents malleability)
  • Are signatures validated against the correct signer?
  • Can a signature be used on a different contract?
  • Can a signature be used on a different chain?
  • Can a signature be used multiple times?
  • Is the signed data correctly encoded (abi.encode vs abi.encodePacked)?
  • → abi.encodePacked can cause hash collisions with dynamic types

16.8 Gas & DoS Checklist

  • Are there unbounded loops?
  • → What is the maximum array size? Can it exceed block gas limit?
  • Are there push patterns that could be DoS'd?
  • → Use pull pattern instead
  • Can ETH be force-sent to break invariants?
  • → Don't rely on address(this).balance == X
  • Can a malicious contract's receive() cause gas griefing?
  • Is there a return bomb risk?
  • → Limit returndata size from external calls
  • Can the contract be permanently DoS'd?
  • Are gas limits set on external calls?
  • Can block stuffing delay time-sensitive operations?

16.9 MEV & Ordering Checklist

  • Are there operations that are profitable to front-run?
  • Are there operations that are profitable to sandwich?
  • Are there operations that depend on transaction ordering?
  • Is there a commit-reveal scheme where needed?
  • Are slippage limits enforced on all swaps?
  • Are deadline parameters enforced?
  • Can a validator manipulate block.timestamp to their advantage?
  • Can a validator manipulate block.prevrandao to their advantage?
  • Are there any operations that should use private mempool?

16.10 Economic Security Checklist

  • What are the protocol's economic invariants?
  • → List them explicitly and verify each one
  • Can a flash loan break any invariant?
  • Can a large deposit/withdrawal break any invariant?
  • Are there any arbitrage opportunities that drain the protocol?
  • Are incentives aligned? (liquidators, arbitrageurs, governance)
  • Can the protocol be drained via repeated small operations?
  • → Rounding errors accumulate
  • Is the protocol solvent under all market conditions?
  • What happens during extreme market volatility?
  • Are there any circular dependencies between protocols?
  • Can the protocol be used to manipulate prices in other protocols?

16.11 Final Pre-Submission Checklist

  • Every finding has a working Foundry PoC
  • Every finding has a clear severity classification
  • Every finding has a quantified impact (dollar amount)
  • Every finding has a specific recommended fix
  • Every finding references the exact file and line number
  • No duplicate findings (each issue is unique)
  • Findings are ordered by severity (Critical first)
  • Executive summary is accurate
  • All contract addresses are correct
  • Fork block number is specified in PoCs
  • PoCs run successfully with: forge test --mt test_finding -vvvv
  • Report is professional and free of typos

16.12 Quick Reference — Vulnerability → Tool Mapping

Vulnerability Best Detection Method
Reentrancy Slither + manual CEI review
Access control Slither + manual function review
Integer overflow Slither (pre-0.8) + manual unchecked review
Oracle manipulation Manual + economic modeling
Flash loan attacks Manual + Foundry fork tests
Signature replay Manual + EIP-712 review
Proxy collision Manual storage layout analysis
Upgradeable bugs Manual + Slither unprotected-upgrade
Token quirks Manual + weird-erc20 checklist
DoS Manual + Foundry gas tests
Precision loss Manual + Foundry fuzz
Governance attacks Manual + economic modeling
MEV/front-running Manual + mempool analysis
Compiler bugs Version check + bytecode verification
ZK circuit bugs Manual circuit review + Halmos

← Previous: Exploit Recreations | Back to Index →

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