web3-audit

> **⚠️ AUTHORIZED USE ONLY**

> This skill is for educational purposes or authorized security assessments only.

> You must have explicit, written permission from the system owner before using this tool.

> Misuse of this tool is illegal and strictly prohibited.

> **Mandatory confirmation gate**

> Before running any command that probes, exploits, changes, persists on, extracts data from, or attempts credential access against a target:

> 1. Ask the user to state the exact target URL, IP, account, or resource.

> 2. Ask the user to confirm written authorization and the permitted scope.

> 3. Show the exact command(s) and explain their expected effect.

> 4. Wait for explicit confirmation in the current conversation.

>

> Without that confirmation, remain read-only and provide defensive guidance only. Prefer a sandbox, disposable VM, or controlled lab.

# WEB3 SMART CONTRACT AUDIT

10 bug classes. Pre-dive kill signals. Foundry PoC template. Real paid examples.

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PRE-DIVE KILL SIGNALS (check BEFORE any code review)

> ZKsync lesson: $322M TVL + OZ audit + 750K LOC + 5 sessions = 0 findings. Large well-audited bridges are extremely hard.

1. **TVL < $500K** → max payout capped too low for effort

2. **2+ top-tier audits** (Halborn, ToB, Cyfrin, OpenZeppelin) on simple protocol → bugs already found

3. **Protocol < 500 lines, single A→B→C flow** → minimal attack surface

4. **Formula**: `max_realistic_payout = min(10% × TVL, program_cap)` — if < $10K, skip

**Soft kill:** OZ/ToB/Cyfrin audit on current version + codebase > 500K LOC → expect 40+ hours for maybe 1 finding. Only proceed if bounty floor > $50K AND you have protocol-specific expertise.

**Target scoring (go if >= 6/10):**

- TVL > $10M: +2

- Immunefi program with Critical >= $50K: +2

- No top-tier audit on current version: +2

- < 30 days since deploy: +1

- Protocol you've hunted before: +1

- Source code + natspec comments: +1

- Upgradeable proxies: +1

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THE ONE RULE

> "Read ALL sibling functions. If `vote()` has a modifier, check `poke()`, `reset()`, `harvest()`. The missing modifier on the sibling IS the bug."

This single rule explains 19% of all Critical findings.

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1. ACCOUNTING STATE DESYNCHRONIZATION

> #1 Critical bug class — 28% of all Criticals on Immunefi.

What It Is

Two state variables supposed to stay in sync. One code path updates A but forgets B. Later code reads both and makes decisions based on stale B.

Real Value = A - B
If A updated but B isn't → Real Value appears larger → phantom value

Root Cause Patterns

**Variant 1: Phantom Yield** (Yeet protocol — 35 duplicate reports)

function startUnstake(uint256 amount) external {
    totalSupply -= amount;  // decremented BEFORE transfer
    // aToken.balanceOf(this) still reflects old value
    // yieldAmount = aToken.balanceOf - totalSupply = phantom yield
}

**Variant 2: Fast Path Skips State Update** (Alchemix V3)

function claimRedemption(uint256 tokenId) external {
    if (transmuter.balance >= amount) {
        transmuter.transfer(user, amount);
        _burn(tokenId);
        return;  // EARLY RETURN — cumulativeEarmarked, _redemptionWeight, totalDebt never updated
    }
    // Slow path: updates all state vars correctly
    alchemist.redeem(...);
}

**Variant 3: Update Happens in Wrong Order** (Alchemix)

function deposit(uint256 amount) external {
    _shares = (amount * totalShares) / totalAssets;  // calculated BEFORE deposit
    totalAssets += amount;   // assets added AFTER shares calculated → wrong rate
}

Grep Patterns

# Find all accounting variables
grep -rn "totalSupply\|totalShares\|totalAssets\|totalDebt\|cumulativeReward\|rewardPerShare" contracts/

# Find all early returns in claim/redeem functions
grep -rn "\breturn\b" contracts/ -B3 | grep -B3 "if\b"

# For each early return: which state updates in normal path are skipped?

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2. ACCESS CONTROL

> #2 Critical — 19% of Criticals. $953M lost i