Bracket receives unlimited StopLimit allowance — AuditVault synthetic reduction

Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 44375-h-5-attacker-can-drain-stoplimit-contract-funds-through-brac. Standalone Foundry PoC and full write-up: 44375-h-5-attacker-can-drain-stoplimit-contract-funds-through-brac_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/logic/missing-allowance · vuln/dependency/unsafe-external-call

Reproduction: self-contained Foundry PoC with an offline synthetic contract. Full trace: output.txt.

AuditVault finding: 44375 · H-5: attacker can drain StopLimit contract funds through Bracket contract because it gives type(uint256).max allowance to bracket contract for input token in performUpkeep function

Key info#


Impact	HIGH — Bracket receives unlimited StopLimit allowance
Protocol	[[Oku'S New Order Types Contract Contest]]
Finding	AuditVault #44375
Report	https://github.com/sherlock-audit/2024-11-oku-judging
Source	AuditVault finding
Compiler	`^0.8.24` (synthetic reduction)
Loss	Reduced invariant reproduced; no live funds moved
Attacker EOA	Configured synthetic caller
Attack contract	`Exploit`
Attack tx	Local Foundry `Exploit.attack()` call
Chain · block · date	Ethereum model · block 1 · synthetic
Vulnerable contract	Local synthetic vulnerable contract in `test/`
Bug class	See vulnerability-class tags above

TL;DR#

This bug report discusses a vulnerability found in a contract called "StopLimit". The issue was discovered by a group of individuals and can be exploited by an attacker to drain funds from the contract. The vulnerability is caused by the contract giving unlimited access to another contract called "Bracket" to transfer tokens from the StopLimit contract. This can be exploited by an attacker by creating an order in the Bracket contract and then calling a function in the StopLimit contract that allows the transfer of tokens. This can be done by setting the target address to the token the attacker wants to transfer and providing the necessary transaction data. The impact of this vulnerability is that an attacker can drain almost all of the funds from the StopLimit contract. The team responsible for the contract has fixed this issue in their code. To prevent similar issues in the future, it i

Background#

The upstream report is a Solidity finding. This page keeps the vulnerable statement and demonstrates its security consequence in a small, deterministic EVM model; no live RPC or external dependencies are required.

The vulnerable code#

SOLIDITY

// The exact vulnerable pattern is retained in test/44375-h-5-attacker-can-drain-stoplimit-contract-funds-through-brac.sol.
// @> see the marked statement in the synthetic reduction

Root cause#

The caller-controlled input or stale state is trusted before the required uniqueness, bounds, authorization, accounting, or reentrancy invariant is enforced. The marked line in the synthetic contract intentionally preserves that ordering so the assertion is executable.

Preconditions#

The vulnerable contract is deployed with the state described by the report.
The attacker can reach the affected entry point (or submit the report's crafted input).

Attack walkthrough#

Exploit.run() initializes the minimal state from the report.
The marked vulnerable operation executes without its required check.
The contract records the resulting invariant violation and emits a Proof event.
The test asserts the harm; the passing trace is recorded at output.txt:4.

Diagrams#

flowchart TD A[Attacker supplies crafted input] --> B[Vulnerable operation] B --> C{Missing invariant check} C --> D[Security impact demonstrated]

sequenceDiagram participant A as Attacker participant V as Vulnerable contract participant S as State A->>V: invoke affected entry point V->>S: apply unchecked update S-->>A: harm is observable

Remediation#

Apply the invariant before mutating state: accrue interest before adding principal; reject duplicate signers; use checked casts and bounded lengths; validate token/target/DAO identities; use nonReentrant; enforce slippage and fee equality; and validate the canonical authority or ownership relationship described by the report.

How to reproduce#

BASH

cd evm-hack-registry/44375-h-5-attacker-can-drain-stoplimit-contract-funds-through-brac_exp
forge test -vvvvv

The test is offline and uses only the shared forge-std library. The corresponding Playground bundle is generated from scripts/poc-configs/44375-h-5-attacker-can-drain-stoplimit-contract-funds-through-brac.mjs.

Sources#

Reference: https://github.com/sherlock-audit/2024-11-oku-judging

Sources & further analysis#

Reproductions & code

Standalone PoC + full trace: 44375-h-5-attacker-can-drain-stoplimit-contract-funds-through-brac_exp (evm-hack-registry mirror).
AuditVault finding: 44375-h-5-attacker-can-drain-stoplimit-contract-funds-through-brac.

Alerts & third-party analyses

Web3Sec X hacked database: search.
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Solodit incident search: search.

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