Yield Strategy Optimization Report: Grove Finance
Target Protocol: Grove Finance (TVL: $1263.6M)
Yield Strategy Optimization Report – Grove Finance
Prepared by: Senior DeFi Security Researcher
Date: 25 September 2026
1. Executive Summary
Grove Finance is a multi‑chain yield‑aggregation platform that currently manages ≈ $1.26 B of TVL across Ethereum L1 and several L2 roll‑ups (Arbitrum, Optimism, zkSync). The protocol offers a suite of “strategies” that automatically allocate user deposits to a hierarchy of external yield‑generating contracts (e.g., lending markets, AMM farms, liquid‑staking derivatives).
Our audit focused on the core strategy router, the strategy contracts, the governance & upgrade mechanisms, and the cross‑chain bridge adapters that move assets between L1 and L2. The goal was to identify technical attack vectors that could jeopardise user capital, degrade yield performance, or undermine the protocol’s trust model, and to provide actionable recommendations that improve both security and economic efficiency.
Key Findings
| Area | Criticality | Summary |
|---|---|---|
| Strategy Upgradeability | High | Unrestricted owner/guardian rights on the StrategyFactory allow arbitrary replacement of any strategy implementation without a timelock. |
| Cross‑Chain Bridge Handlers | High | Insufficient replay‑protection and missing “canonical‑token” verification on L2 adapters expose the system to double‑spend and token‑mis‑routing attacks. |
| External Protocol Integration | Medium | Strategies rely on a single external contract (e.g., a single Curve pool) without fallback paths; a failure or malicious upgrade of that external contract can freeze funds. |
| Re‑entrancy in Harvest/Withdraw | Medium | Harvest functions call external reward contracts before updating internal accounting, opening a classic re‑entrancy window. |
| Oracle & Price‑Feed Manipulation | Medium | Some strategies use on‑chain TWAPs from low‑liquidity pools for slippage checks; price manipulation can trigger premature liquidations or sub‑optimal rebalancing. |
| Governance Token Lock‑up & Vote‑Escrow | Low | The veGRO lock‑up contract does not enforce a minimum lock period for voting power, allowing flash‑vote attacks. |
| Gas‑Optimization & DoS Vectors | Low | Certain loops over dynamic arrays (e.g., strategyList) are unbounded, potentially causing out‑of‑gas reverts under heavy load. |
Overall, the protocol’s technical risk score is 6.4 / 10 (moderate‑high). The most urgent remediation is to tighten upgrade governance and bridge security, followed by hardening re‑entrancy and price‑oracle usage.
2. Identified Attack Vectors
| # | Vector | Affected Contracts | Attack Description | Potential Impact |
|---|---|---|---|---|
| 1 | Unrestricted Strategy Upgrade |
StrategyFactory, StrategyProxy
|
The owner (or a single guardian address) can call upgradeStrategy(address newImpl) without a timelock or multi‑sig. An attacker who compromises the owner key can replace any strategy with a malicious implementation that siphons funds or emits false rewards. |
Full loss of assets allocated to the compromised strategy (potentially > $300 M). |
| 2 | Bridge Replay / Token‑Mis‑routing |
L1BridgeAdapter, L2BridgeAdapter (Arbitrum, Optimism, zkSync) |
Bridge adapters accept a nonce from the L2 message but do not verify that the nonce is unique per token pair. A malicious relayer can replay a successful deposit message on a different L2, causing duplicate minting of wrapped tokens. |
Inflation of wrapped assets, dilution of existing holders, and possible arbitrage attacks. |
| 3 | Single‑Point External Dependency |
StrategyCurve3Pool, StrategyAaveV3
|
Strategies call a single external pool contract for deposits/withdrawals. If that pool is paused, upgraded to a malicious version, or suffers a bug, the strategy’s funds become locked. | Funds frozen for the duration of the external incident; could be days to weeks, eroding user confidence. |
| 4 | Re‑entrancy in Harvest/Withdraw |
BaseStrategy, RewardDistributor
|
harvest() first calls rewardToken.claim() and then updates totalStaked. A malicious reward token that implements a callback can re‑enter harvest() and double‑count rewards, inflating the internal balance and allowing the attacker to withdraw excess tokens. |
Over‑payment of rewards, loss of up to the total reward pool (estimated $10‑15 M). |
| 5 | Manipulable On‑Chain Price Oracles |
StrategyBalancer, StrategyLido
|
Slippage checks use TWAP from a low‑liquidity Uniswap v3 pool (e.g., 0.01% fee tier). An attacker can front‑run a large swap to distort the TWAP, causing the strategy to believe a token is under‑priced and trigger a re‑balance that moves capital into a low‑yield, high‑risk position. | Sub‑optimal yield, potential exposure to a failing external protocol, indirect capital loss. |
| 6 | Flash‑Vote / Governance Capture |
veGRO, GroveGovernor
|
veGRO allows users to lock tokens for any duration ≥ 1 day. An attacker can acquire a large amount of GRO, lock for 1 day, vote, and then unlock immediately after the proposal passes, repeating the cycle. |
Governance proposals can be passed with minimal economic cost, enabling malicious parameter changes (e.g., fee reductions, upgrade approvals). |
| 7 | Unbounded Loops / DoS |
StrategyRouter, GroveTreasury
|
Functions such as rebalanceAll() iterate over strategyList without a cap. An attacker can add a large number of dummy strategies (via addStrategy) and force the router to exceed block gas limits, halting rebalancing and harvest cycles. |
Service denial, delayed reward distribution, increased gas costs for honest users. |
| 8 | Insufficient Access Controls on Emergency Pause | GrovePauseManager |
The pause() function can be called by any address that holds ≥ 0.5 % of total GRO (via a “soft‑pause” guard). A coordinated flash‑loan attack could temporarily acquire enough GRO to trigger a pause, freezing the protocol during a market crash. |
Market panic, loss of user confidence, potential arbitrage on frozen assets. |
3. Prioritized Technical Recommendations
| Priority | Recommendation | Rationale | Implementation Sketch |
|---|---|---|---|
| Critical | Introduce a Multi‑Sig Timelocked Upgrade Path for Strategies | Removes single‑point control and gives users a window to react to malicious upgrades. | Deploy a StrategyGovernor (e.g., Gnosis Safe + 48‑hour delay) that owns the StrategyFactory. Replace direct owner calls with onlyGovernor. Add upgradeProposal event and executeUpgrade after delay. |
| Critical | Add Replay‑Protection & Canonical Token Verification to Bridge Adapters | Prevents double‑minting and token‑mis‑routing across L1/L2. | Store a mapping bytes32 => bool processed keyed by keccak256(chainId, txHash, nonce, token). Reject any message with a processed key. Verify that the token address on L2 matches the canonical token list stored on L1. |
| High | Implement Fallback / Redundancy for External Protocol Calls | Mitigates single‑point failure of external pools. | In each strategy, maintain an ordered list of approved external contracts. On failure of the primary, automatically fallback to the next. Emit FallbackUsed(strategy, fallbackAddress). |
| High | Re‑order State Updates to Prevent Re‑entrancy | Classic mitigation; eliminates reward double‑counting. | In harvest() and withdraw(), update internal accounting (totalStaked, rewardDebt) before external calls. Use the Checks‑Effects‑Interactions pattern or OpenZeppelin’s ReentrancyGuard. |
| Medium | Replace Low‑Liquidity TWAP Oracles with Robust Aggregators | Reduces price manipulation surface. | Integrate Chainlink or DIA price feeds for high‑value assets. For assets without feeds, use a weighted TWAP across multiple pools (different fee tiers, DEXes). Add a maxPriceDeviation guard. |
| Medium | Enforce Minimum Lock Duration for veGRO Voting Power | Discourages flash‑vote attacks. | Require lockDuration >= 7 days for any lock that contributes voting power. Adjust veGRO contract to reject shorter locks or to apply a penalty multiplier for short locks. |
| Low | Cap Dynamic Arrays & Add Pagination for Loops | Prevents DoS via gas exhaustion. | Introduce a MAX_STRATEGIES = 50 constant. In addStrategy, revert if strategyList.length >= MAX_STRATEGIES. Provide viewStrategy(uint256 start, uint256 count) for pagination. |
| Low | Hard‑code Emergency Pause Authority to a Timelocked Multi‑Sig | Removes soft‑pause abuse via token‑holding thresholds. | Deploy a PauseGuardian (Gnosis Safe) with a 24‑hour timelock for pause()/unpause(). Remove the token‑balance guard. |
| Optional | Add Automated Monitoring & Alerting | Early detection of abnormal behavior. | Deploy a Sentinel bot that watches for: (i) sudden spikes in upgradeStrategy calls, (ii) bridge message replays, (iii) large slippage events. Integrate with PagerDuty/Discord. |
| Optional | Formal Verification of Core Math (e.g., reward accrual) | Guarantees correctness of reward calculations. | Use Certora or Slither‑Prover to verify invariants: totalRewardsDistributed ≤ totalRewardsClaimed + totalRewardsPending. |
Implementation Timeline (Suggested)
| Weeks | Milestones |
|---|---|
| 0‑2 | Deploy multi‑sig governance for StrategyFactory; freeze direct owner upgrades. |
| 2‑4 | Add replay‑protection to bridge adapters; run integration tests on all L2s. |
| 4‑6 | Refactor harvest()/withdraw() with re‑entrancy guard; add fallback lists to strategies. |
| 6‑8 | Replace vulnerable TWAPs with Chainlink/DIA feeds; add price‑deviation checks. |
| 8‑10 | Enforce minimum lock duration in veGRO; adjust UI/Docs. |
| 10‑12 | Cap strategy arrays, add pagination, and harden emergency pause. |
| 12‑16 | Deploy monitoring bots; optional formal verification. |
4. Risk Score
| Dimension | Score (1‑10) | Comments |
|---|---|---|
| Smart‑Contract Code Quality | 6 | Mostly solid, but several re‑entrancy and upgradeability issues. |
| Governance & Upgrade Model | 8 | Centralized upgrade authority without timelock is the biggest risk. |
| Cross‑Chain Bridge Security | 7 | Replay‑attack surface and lack of canonical token checks. |
| External Dependency Resilience | 5 | Heavy reliance on single external pools; no fallback. |
| Economic Attack Surface (oracles, voting) | 5 | Price manipulation possible; veGRO lock‑duration too permissive. |
| Denial‑of‑Service (DoS) Vectors | 4 | Unbounded loops could be abused, but impact limited. |
| Overall Composite Risk | 6.4 / 10 | Moderate‑high. The protocol is functional and audited, but the identified high‑severity vectors must be mitigated before further TVL growth. |
Scoring methodology follows a weighted average (weights: code 30 %, governance 30 %, bridge 20 %, external 10 %, economic 5 %, DoS 5 %).
5. Conclusion
Grove Finance has built a compelling yield‑aggregation product that already commands >$1.2 B in assets. The core architecture—strategy router → strategy contracts → external protocols—is sound, and the codebase follows many industry best practices (use of OpenZeppelin libraries, modular design, and extensive unit tests).
However, the upgradeability and cross‑chain bridge mechanisms constitute the most critical attack surface. An adversary who gains control of the current owner or a bridge relayer could exfiltrate a substantial portion of the TVL or create token inflation scenarios. Additionally, re‑entrancy and price‑oracle manipulation present exploitable weaknesses that could erode user yields and trust.
By implementing the prioritized recommendations—especially the multi‑sig timelocked upgrade governance, robust bridge replay protection, and re‑ordering of state updates—the protocol can reduce its composite risk score from 6.4 to ≤ 3.5, positioning Grove Finance as a high‑assurance platform suitable for continued TVL expansion and institutional onboarding.
We recommend that Grove Finance:
- Adopt the critical recommendations within the next 8‑12 weeks (upgrade governance, bridge hardening, re‑entrancy fixes).
- **Publish a transparent upgrade‑process roadmap
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