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Reproduced Exploit

OracleLess executes attacker-controlled target — AuditVault synthetic reduction

The OracleLess contract has a vulnerability that allows attackers to drain all USDT from the contract. This is caused by the createOrder() function not verifying if the tokenIn is a legitimate ERC20 token and the fillOrder() function not checking if the target and txData are valid. This allows atta…

Nov 2024•Other•access-control•3 min read

Chain

Other

Category

access-control

Date

Nov 2024

Source

AuditVault

PoC & write-upPoC for your local evm-hack-analyzerAuditVault PoCs

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The attack is replayed in an in-browser EVM preloaded with the exact dumped fork state. The execution tree shows every call; step by Solidity line or by opcode across all depths — source, Stack, Memory, Storage, Balances (native / ERC-20 / NFT), Transient storage and Return value stay in sync. Click a tree node, opcode, or source line to jump. No backend, no live RPC.

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Source & credit. Reproduction of a public audit finding curated by AuditVault — the original finding: 44372-h-2-attackers-can-drain-the-oracleless-contract-by-creating. Standalone Foundry PoC and full write-up: 44372-h-2-attackers-can-drain-the-oracleless-contract-by-creating_exp in the evm-hack-registry mirror.

Vulnerability classes: vuln/access-control/missing-auth · vuln/dependency/unsafe-external-call

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

AuditVault finding: 44372 · H-2: Attackers can drain the OracleLesscontract by creating an order with amalicious tokenInand executing it with amalicious target.

Key info#

ImpactHIGH — OracleLess executes attacker-controlled target
Protocol[[Oku'S New Order Types Contract Contest]]
FindingAuditVault #44372
Reporthttps://github.com/sherlock-audit/2024-11-oku-judging
SourceAuditVault finding
Compiler^0.8.24 (synthetic reduction)
LossReduced invariant reproduced; no live funds moved
Attacker EOAConfigured synthetic caller
Attack contractExploit
Attack txLocal Foundry Exploit.attack() call
Chain · block · dateEthereum model · block 1 · synthetic
Vulnerable contractLocal synthetic vulnerable contract in test/
Bug classSee vulnerability-class tags above

TL;DR#

The OracleLess contract has a vulnerability that allows attackers to drain all USDT from the contract. This is caused by the createOrder() function not verifying if the tokenIn is a legitimate ERC20 token and the fillOrder() function not checking if the target and txData are valid. This allows attackers to create an order with a malicious token and execute it with a malicious target and txData, resulting in all USDT being transferred to the attacker. A recommended solution is to implement a whitelist mechanism for token, target, and txData to prevent this vulnerability.

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/44372-h-2-attackers-can-drain-the-oracleless-contract-by-creating.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#

  1. Exploit.run() initializes the minimal state from the report.
  2. The marked vulnerable operation executes without its required check.
  3. The contract records the resulting invariant violation and emits a Proof event.
  4. 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/44372-h-2-attackers-can-drain-the-oracleless-contract-by-creating_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/44372-h-2-attackers-can-drain-the-oracleless-contract-by-creating.mjs.

Sources#

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

Sources & further analysis#

Reproductions & code

Alerts & third-party analyses

  • Web3Sec X hacked database: search.
  • Rekt leaderboard: search.
  • Solodit incident search: search.

These dashboards index community alerts tweets, post-mortems, and independent write-ups. Reach them through the protocol name above to cross-check this reproduction against other analyses.