Security Audit Report: Reentrancy & Access Control Review: Gauntlet
Target Protocol: Gauntlet (TVL: $1644.4M)
Security Audit Report – Reentrancy & Access‑Control Review
Protocol: Gauntlet
Scope: Core smart‑contract suite (Ethereum mainnet & L2 roll‑ups) – Vaults, Strategy Manager, Fee Distributor, Governance & Upgrade Proxy layers.
Date of Review: 2026‑09‑30 – 2026‑10‑05
Auditors: Senior DeFi Security Research Team – [Your Company]
1. Executive Summary
Gauntlet is a high‑TVL ($1.64 B) asset‑management and yield‑optimization protocol that operates on Ethereum L1 and several L2s (Arbitrum, Optimism, zkSync). The platform’s core value proposition relies on automated strategy execution, dynamic fee distribution, and on‑chain governance.
Our focused audit examined reentrancy safety and access‑control robustness across the entire contract suite, with special attention to:
| Component | Primary Function | Criticality (1‑5) |
|---|---|---|
| VaultCore | Deposits/withdrawals, share accounting | 5 |
| StrategyManager | Deploys/updates external strategy contracts | 5 |
| FeeDistributor | Calculates & distributes protocol fees | 4 |
| GovernanceProxy | Upgradeable proxy & timelock | 5 |
| RoleManager (OpenZeppelin AccessControl) | Role assignment & admin functions | 4 |
Key Findings
| Category | # of Issues | Severity (Critical/High/Medium/Low) |
|---|---|---|
| Reentrancy | 3 | 2 Critical, 1 High |
| Access‑Control | 5 | 1 Critical, 2 High, 2 Medium |
| Overall Risk Score | – | 7.2 / 10 |
The critical reentrancy issues stem from unprotected external calls in the VaultCore.withdraw() path and in the strategy harvest flow, where state updates occur after an external call. The critical access‑control flaw is an unrestricted upgrade path in the GovernanceProxy that can be triggered by any address holding the PROPOSER_ROLE without a timelock safeguard.
If exploited, these vulnerabilities could enable an attacker to drain vault assets, steal accrued fees, or freeze protocol upgrades, potentially resulting in loss of >$300 M in assets under management (AUM).
The remainder of the findings are high‑impact but mitigable with standard best‑practice patterns (checks‑effects‑interactions, reentrancy guards, principle‑of‑least‑privilege role design, and timelock enforcement).
2. Identified Attack Vectors
2.1 Reentrancy Vulnerabilities
| # | Contract / Function | Description | Exploit Scenario | Potential Impact |
|---|---|---|---|---|
| R‑1 | VaultCore.withdraw(uint256 amount) |
The function transfers ERC‑20 tokens before updating the user’s share balance and total supply. The external token contract may be malicious (e.g., a wrapped token with a transfer hook) and re‑enter withdraw() to claim additional shares. |
Attacker deposits a malicious ERC‑20, then calls withdraw(). The token’s transfer callback re‑enters withdraw(), causing the protocol to credit the attacker with extra shares before the original balance is reduced. |
Unlimited token extraction from the vault; loss of user funds proportional to vault TVL. |
| R‑2 | StrategyManager.harvest(address strategy) |
Harvest calls strategy.claimRewards() (external) before updating the internal lastHarvest timestamp and reward accounting. A malicious strategy can re‑enter harvest() and claim rewards repeatedly within the same block. |
Attacker deploys a rogue strategy contract that, on claimRewards(), calls back into StrategyManager.harvest() via a low‑level call. The protocol credits rewards multiple times before the timestamp is set. |
Inflation of reward tokens, dilution of existing LPs, and potential loss of protocol fee revenue. |
| R‑3 | FeeDistributor.distribute(address token) |
The function iterates over a list of beneficiaries and performs token.transfer(beneficiary, amount) before marking the distribution as completed. A malicious ERC‑20 with a transfer hook can re‑enter distribute() and cause double‑payouts. |
Attacker creates a malicious ERC‑20 that, on transfer, calls back into FeeDistributor.distribute() for the same token, resetting the internal distributed flag. |
Over‑distribution of fees, leading to excess token outflow and potential tokenomics disruption. |
2.2 Access‑Control Weaknesses
| # | Contract / Function | Description | Exploit Scenario | Potential Impact |
|---|---|---|---|---|
| A‑1 (Critical) | GovernanceProxy.upgradeTo(address newImplementation) |
The upgrade function is gated only by PROPOSER_ROLE. The role is granted to any address that holds a minimum amount of the protocol’s governance token (≥ 0.1 % of supply). No timelock is enforced, allowing immediate upgrades. |
An attacker accumulates the required token amount (or borrows via flash loan) and calls upgradeTo() with a malicious implementation that includes a backdoor. |
Full control over all protocol logic; ability to siphon assets, freeze withdrawals, or mint tokens. |
| A‑2 | RoleManager.grantRole(bytes32 role, address account) |
The admin role (DEFAULT_ADMIN_ROLE) is assigned to the TimelockController and to the MultisigWallet. However, the MultisigWallet is a 2‑of‑3 wallet where one signer is a cold‑storage address that has been inactive for > 180 days. |
If the inactive signer’s key is compromised, an attacker can push a malicious transaction through the multisig, granting themselves PROPOSER_ROLE or DEFAULT_ADMIN_ROLE. |
Escalation to full admin rights, enabling any of the above upgrade attacks. |
| A‑3 | StrategyManager.setStrategy(address token, address strategy) |
Only STRATEGIST_ROLE can call, but the role is granted to any address that has ever interacted with the VaultCore (i.e., any depositor). |
A regular user can replace a legitimate strategy with a malicious contract that steals deposited assets during the next harvest. | Loss of funds allocated to the compromised strategy; potential cascade if the strategy holds other protocol assets. |
| A‑4 | FeeDistributor.setBeneficiary(address beneficiary, uint256 share) |
No explicit access restriction; function is external and can be called by anyone. |
An attacker adds themselves as a beneficiary with a large share, inflating their portion of fee distribution. | Dilution of legitimate beneficiaries, revenue loss. |
| A‑5 | VaultCore.setDepositCap(uint256 newCap) |
Callable by CAP_MANAGER_ROLE. The role is granted to a single externally‑owned account (EOA) without any multi‑sig or timelock. |
An attacker who compromises the EOA can lower the cap to zero, effectively freezing deposits, or raise it to an arbitrarily high value, enabling a flash‑loan attack that overwhelms the vault’s risk parameters. | Operational disruption, potential for liquidity‑drain attacks. |
3. Prioritized Technical Recommendations
3.1 Reentrancy Mitigations
| Priority | Recommendation | Rationale | Implementation Notes |
|---|---|---|---|
| P1 |
Add nonReentrant (OpenZeppelin) or custom reentrancy guard to all external‑call‑heavy functions: withdraw(), harvest(), distribute(). |
Guarantees that a re‑entrant call cannot re‑enter the same function within the same transaction. | Use ReentrancyGuard with _status pattern; ensure the guard is placed before any external calls. |
| P2 | Apply Checks‑Effects‑Interactions (CEI) pattern – move all state updates before token transfers or external calls. | Even with a guard, CEI eliminates the window for re‑entrancy attacks. | Refactor withdraw() to: 1️⃣ validate amount, 2️⃣ update userShares & totalSupply, 3️⃣ emit events, 4️⃣ transfer tokens. |
| P3 |
Whitelist ERC‑20 tokens for vault deposits/withdrawals, or enforce IERC20Metadata.decimals() sanity checks. |
Prevents malicious tokens with overridden transfer/transferFrom that execute callbacks. |
Maintain a mapping(address => bool) public allowedTokens; with admin‑controlled updates. |
| P4 |
Introduce a “harvest lock” – a per‑strategy bool harvesting flag that blocks concurrent harvests and resets after the function completes. |
Stops recursive re‑entry via claimRewards() while still allowing legitimate sequential harvests. |
Set harvesting = true at entry, harvesting = false on exit (use try/catch to guarantee reset). |
| P5 |
Add a “distribution lock” for FeeDistributor similar to the harvest lock, or batch payouts off‑chain with Merkle proofs. |
Reduces on‑chain exposure to re‑entrancy during mass token transfers. | Consider moving to a Merkle‑tree based claim system for large beneficiary sets. |
3.2 Access‑Control Hardenings
| Priority | Recommendation | Rationale | Implementation Notes |
|---|---|---|---|
| P1 |
Upgrade Path Must Use Timelock – GovernanceProxy.upgradeTo() should be callable only by the TimelockController (or a multisig) with a minimum delay (≥ 48 h). |
Removes instant upgrade capability, mitigating flash‑loan or short‑term token‑holding attacks. | Replace onlyRole(PROPOSER_ROLE) with onlyRole(TIMELOCK_ROLE). Ensure the timelock enforces delay and gracePeriod. |
| P2 |
Restrict PROPOSER_ROLE to a DAO‑controlled multisig (e.g., Gnosis Safe 3‑of‑5) rather than token‑based thresholds. |
Token‑based role assignment is vulnerable to market manipulation and flash‑loan acquisition. | Revoke existing PROPOSER_ROLE from token‑holders; grant to the DAO safe address. |
| P3 | Implement Role‑Renouncement & Rotation – add functions to safely rotate admin keys, with a 2‑day timelock and event logging. | Reduces risk from stale or compromised keys (e.g., inactive cold‑storage signer). | Use grantRole/revokeRole only via timelock; emit RoleRenounced(address indexed account, bytes32 role). |
| P4 |
Restrict setStrategy to a dedicated STRATEGY_ADMIN_ROLE that is not automatically granted to depositors. |
Prevents arbitrary users from swapping out strategies. | Remove grantRole(STRATEGIST_ROLE, address) from depositor onboarding; keep a whitelist of vetted strategy contracts. |
| P5 |
Add access control to FeeDistributor.setBeneficiary – only FEE_ADMIN_ROLE (multisig) may modify beneficiaries. |
Stops arbitrary fee siphoning. | Add onlyRole(FEE_ADMIN_ROLE) modifier. |
| P6 |
Migrate CAP_MANAGER_ROLE to a multisig with a timelock – or make the cap immutable after initial deployment if business logic permits. |
Prevents single‑point compromise from freezing or over‑exposing the vault. | Deploy a new CapManager contract behind a proxy, controlled by DAO. |
| P7 | Perform a comprehensive role‑audit – generate a matrix of all roles, their admins, and current holders; ensure the principle of least privilege. | Guarantees no hidden privilege escalation paths remain. | Use scripts (e.g., hardhat-access-control-audit) and publish the matrix in the repo. |
| P8 | Add event emission for all critical admin actions (upgrades, role grants/revokes, cap changes). | Improves on‑chain observability and enables rapid detection of malicious changes. | Follow OpenZeppelin’s AccessControl events; add custom CapChanged(uint256 oldCap, uint256 newCap). |
3.3 Additional Defensive Measures
| Priority | Recommendation | Rationale |
|---|---|---|
| P1 |
Deploy a “Reentrancy Testnet” – a forked mainnet environment with malicious ERC‑20 tokens (e.g., ReentrancyToken) to run integration tests against the updated contracts. |
Guarantees that the CEI and guard changes close the identified attack windows. |
| P2 |
Formal verification of the upgradeability pattern – use tools like Certora or Slither‑Prover to prove that upgradeTo cannot be called without the timelock. |
Provides mathematical assurance for the most critical upgrade path. |
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