Rugproof Audit — examples/VulnerableVault.sol

2026-05-13 · commit HEAD · local

Summary

VulnerableVault is a 56-line ETH custody contract with a classic fund-draining reentrancy in withdraw() exploitable in a single tx, two privileged functions lacking access control, an unchecked external call, and an EOA admin with sweep authority. Not safe to deploy.

Critical

High

Medium

Low

Info

Trust report

transferOwnership — Immediate owner rotation with no two-step (Authority: single EOA; Timelock: none)
rescue — Owner can transfer entire contract balance anywhere (Authority: single EOA; Timelock: none)
setPaused — Pause flag with no access control (Authority: anonymous; Timelock: none)

Findings

REENT-001 Critical Reentrancy drains vault via CEI violation

Location

examples/VulnerableVault.sol:24

Summary

withdraw() sends ether before zeroing balance; attacker re-enters via receive() to drain the vault.

Code

function withdraw() external {
    uint256 amt = balance[msg.sender];
    (bool ok,) = msg.sender.call{value: amt}("");
    require(ok);
    balance[msg.sender] = 0;
}

Impact

Loss of 100% of user deposits in one tx. PoC demonstrates 1 ETH attacker → 11 ETH withdrawn.

Recommendation

Move state update before the external call (CEI). Or add nonReentrant.

Suggested patch

-    (bool ok,) = msg.sender.call{value: amt}("");
-    require(ok);
-    balance[msg.sender] = 0;
+    balance[msg.sender] = 0;
+    (bool ok,) = msg.sender.call{value: amt}("");
+    require(ok);

ACCESS-001 High setPaused has no access control

Location

examples/VulnerableVault.sol:34

Summary

Anyone can call setPaused(bool) — pause state controllable by adversary.

Code

function setPaused(bool p) external { paused = p; }

Impact

State pollution today; full DoS if any future function gains whenNotPaused gating.

Recommendation

Add onlyOwner modifier.

ACCESS-002 High rescue can drain user deposits

Location

examples/VulnerableVault.sol:40

Summary

Owner can transfer entire contract balance (= user deposits) anywhere with no allowlist or timelock.

Code

function rescue(address payable to) external onlyOwner { to.transfer(address(this).balance); }

Impact

Single-key compromise = 100% user fund loss.

Recommendation

Remove or scope to non-deposit assets; add Timelock + multi-sig.

UNCHK-001 High Low-level call return value ignored

Location

examples/VulnerableVault.sol:46

Summary

depositor.call(data) silently swallows failure.

Code

depositor.call(data);

Impact

Silent notification failures; gas-grief surface.

Recommendation

Capture return value; require(ok).

CENT-001 Medium Single-EOA owner with no two-step transfer

Location

examples/VulnerableVault.sol:50

Summary

transferOwnership applies immediately; typo can permanently brick contract.

Code

function transferOwnership(address newOwner) external onlyOwner { owner = newOwner; }

Impact

Operational risk on owner rotation.

Recommendation

Use Ownable2Step.

PRAGMA-001 Low Floating pragma ^0.8.20

Location

examples/VulnerableVault.sol:2

Summary

Pin compiler version to match audited bytecode.

Code

pragma solidity ^0.8.20;

Impact

Future minor compiler updates can change codegen.

Recommendation

pragma solidity 0.8.24;