Yield Strategy Optimization Report: Sentora Curator

Target Protocol: Sentora Curator (TVL: $2356.5M)

Yield Strategy Optimization Report – Sentora Curator

Protocol: Sentora Curator (TVL: $2,356.5 M across Ethereum and L2s)

Date: 28 September 2026

Prepared by: [Your Name], Senior DeFi Security Researcher & Smart‑Contract Auditor

1. Executive Summary

Sentora Curator is a multi‑chain yield‑optimisation platform that aggregates user deposits, allocates capital across a dynamic set of “strategies” (e.g., lending, AMM liquidity, staking, and Layer‑2 roll‑up farms) and automatically re‑balances to maximise APR while preserving capital safety. The protocol’s core contracts consist of:

Component	Primary Functions	Key External Interfaces
Vault	Deposit/withdraw, share‑minting, fee accounting	ERC‑20 token, `receive()`
StrategyRouter	Selects optimal strategy per asset, triggers re‑balance, monitors health	Strategy contracts, price oracles, Chainlink, Gelato Keepers
StrategyBase (abstract)	`deposit()`, `withdraw()`, `harvest()`, `emergencyWithdraw()`	Underlying protocol contracts (Aave, Compound, Uniswap V3, L2 farms)
Governance	Parameter updates, strategy whitelist, fee changes	Timelock, DAO voting contracts
OracleAggregator	Consolidates price feeds, slippage limits, TVL snapshots	Chainlink, Band, custom off‑chain reporters
SecurityModule	Re‑entrancy guard, pause, role‑based access control (RBAC)	OpenZeppelin `AccessControl`, `Pausable`

The platform’s TVL of $2.36 B places it among the top‑10 yield aggregators, making it a high‑value target for adversaries. Our audit focused on the Ethereum mainnet deployment (the reference implementation) and the L2 bridge contracts that enable cross‑chain capital flows. The analysis combines static code review, formal verification of critical invariants, runtime simulation with Foundry/Hardhat, and threat‑model mapping against the STRIDE framework (Spoofing, Tampering, Repudiation, Information disclosure, Denial‑of‑service, Elevation of privilege).

Overall Risk Assessment

Metric	Rating (1‑10)	Rationale
Smart‑contract attack surface	7	Complex routing logic, multiple external calls, and upgradeable proxies increase exposure.
Economic attack surface	8	Large capital pool, dynamic APR incentives, and fee‑distribution mechanisms create profitable MEV and flash‑loan vectors.
Governance & upgradeability	6	Timelock (48 h) mitigates rushed changes, but role‑concentration (single “Strategist” address) raises insider risk.
Cross‑chain bridge	7	L2‑to‑Ethereum message verification relies on a single aggregator contract; any compromise could lead to asset loss.
Composite risk score	7.2 (rounded to 7)	The protocol is high‑risk and warrants immediate remediation of the highest‑severity findings.

The remainder of this report details the identified attack vectors, technical recommendations, and a prioritised remediation roadmap.

2. Identified Attack Vectors

#	Attack Vector	Severity*	Likelihood	Impact	Description	Exploitable Path
A1	Re‑entrancy in `StrategyRouter.rebalance()`	High (9)	Medium	Critical loss of user funds	The router calls `strategy.withdraw()` → external protocol callback → re‑enters `rebalance()` before the internal accounting (`totalAssets`) is updated.	Flash‑loan attacker can force partial withdrawals, manipulate share price, and extract excess assets.
A2	Oracle manipulation / price‑feed lag	High (8)	High	Mis‑allocation of capital, arbitrage loss	`OracleAggregator` aggregates three feeds but uses a simple median without sanity checks on timestamp drift. An attacker can feed stale data to a single feed, causing the median to shift and trigger a sub‑optimal strategy switch.	Front‑running or bribing a Chainlink node; can be combined with flash‑loan to harvest profit.
A3	Unrestricted `Strategist` role	Medium‑High (7)	Low‑Medium	Governance takeover, fee‑drain	The `Strategist` role (ability to add/remove strategies) is granted to a single EOA without multi‑sig. If the private key is compromised, the attacker can whitelist a malicious strategy that siphons assets.	Private‑key leak, social engineering, or phishing.
A4	Improper handling of `emergencyWithdraw()` on failing strategies	High (8)	Medium	Permanent loss of assets locked in a failing strategy	Some strategies (e.g., L2 farms) do not implement a safe `emergencyWithdraw()` fallback; the router assumes success and updates `totalAssets` regardless. If the call reverts, the vault’s accounting diverges from reality, leading to share‑price distortion.	Attackers can trigger a forced `emergencyWithdraw()` during a network congestion event to cause a revert.
A5	Cross‑chain bridge replay / message‑ordering attack	High (8)	Medium	Double‑spend of bridged assets	The L2‑to‑Ethereum bridge uses a single `MessageVerifier` contract that only checks the Merkle proof but not the message nonce against a per‑sender monotonic counter. An attacker can replay a previously verified withdrawal message on Ethereum after a fork or after a state‑reset on L2.	Replay via a compromised L2 operator or a malicious sequencer.
A6	Gas‑price manipulation leading to “sandwich” on `deposit()`	Medium (6)	High	User receives lower APR, protocol fee loss	`deposit()` calculates expected share price based on the current `totalAssets`. An attacker can front‑run a large deposit with a high‑gas transaction that temporarily inflates `totalAssets`, causing subsequent users to receive fewer shares.	Classic sandwich attack using Flashbots or private relays.
A7	Denial‑of‑service via unbounded loops in `StrategyRouter.harvestAll()`	Medium (5)	Medium	Halt of yield collection, APR drop	`harvestAll()` iterates over an unbounded array of strategies. If an attacker adds a large number of dummy strategies (each with zero balance), the function can exceed block gas limits, preventing any harvest.	Abuse of the `addStrategy()` function (requires `Strategist` role).
A8	Incorrect ERC‑20 `permit` handling in `Vault`	Low‑Medium (4)	Low	Unauthorized token transfer	The vault supports `permit()` for gas‑less approvals but does not verify the `deadline` correctly when the signature is from a contract wallet (EIP‑1271). This can be abused to replay a permit after the deadline.	Exploit via a contract wallet that signs a permit with a far‑future deadline.
A9	Insufficient pause granularity	Low (3)	Low	Inability to isolate faulty component	The `Pausable` implementation pauses the entire protocol, not individual strategies. In the event of a single compromised strategy, the whole system must be halted, increasing operational risk.	Not an exploit per se, but a design weakness.

*Severity is expressed on a 1‑10 scale (10 = catastrophic).

2.1 Detailed Technical Findings

A1 – Re‑entrancy in `StrategyRouter.rebalance()`

Root cause: The router updates totalAssets after calling external strategy.withdraw() and strategy.deposit(). The external protocol (e.g., Aave) invokes a callback (onWithdraw) that can call back into the router (via a malicious strategy contract).
Impact: An attacker can repeatedly withdraw a fraction of assets, mint extra shares, and re‑deposit, inflating the vault’s share price while siphoning the excess.
Evidence: Unit‑test simulation with a malicious StrategyMock that re‑enters rebalance() caused totalAssets to be double‑counted.

A2 – Oracle Manipulation

Root cause: OracleAggregator.getPrice() computes the median of three feeds but does not enforce a maximum timestamp delta (maxStale = 30 min). A compromised feed can publish a stale price that becomes the median if the other two feeds are temporarily delayed (e.g., due to network congestion).
Impact: The router may allocate capital to a low‑yield or high‑risk strategy based on a manipulated price, exposing users to loss.

A3 – Unrestricted `Strategist` Role

Root cause: The Strategist role is granted via grantRole(STRATEGIST_ROLE, <EOA>) in the constructor and never transferred to a multi‑sig. The role has addStrategy, removeStrategy, and setStrategyParams.
Impact: A single compromised key gives an attacker the ability to whitelist a malicious strategy that implements deposit() as a token sweep.

A4 – Emergency Withdraw Failure Handling

Root cause: StrategyRouter._handleEmergencyWithdraw(address strategy) calls strategy.emergencyWithdraw() inside a try/catch. On failure, the router still updates totalAssets assuming the assets were returned.
Impact: The vault’s accounting diverges, leading to an inflated pricePerShare. Subsequent withdrawals will over‑pay the attacker.

A5 – Bridge Replay Vulnerability

Root cause: The bridge’s MessageVerifier.verifyMessage(bytes calldata proof, bytes calldata data) checks Merkle proof validity but does not store a per‑sender nonce. The MessageProcessor only checks that the message hash has not been processed before, but the hash does not include the L2 block number.
Impact: An attacker can replay a previously verified withdrawal after a L2 chain re‑org or after a forced state reset, effectively double‑spending the bridged assets.

A6 – Sandwich on Deposit

Root cause: Vault.deposit(uint256 amount) calculates shares = amount * totalSupply / totalAssets before the external transferFrom. An attacker can front‑run a large deposit, temporarily inflate totalAssets, causing the victim’s share calculation to be unfavorable.

A7 – Unbounded Harvest Loop

Root cause: StrategyRouter.harvestAll() loops over strategies.length. No cap or pagination is enforced. Adding many dummy strategies (each with zero balance) can cause the transaction to exceed the block gas limit.

A8 – Permit Replay

Root cause: The Vault.permit() implementation uses ecrecover without checking deadline against the current block timestamp when the signature originates from a contract (EIP‑1271).

A9 – Pause Granularity

Root cause: The Pausable modifier is applied at the contract level (Vault, StrategyRouter). Individual strategies cannot be paused independently, forcing a full protocol halt for a single compromised component.

3. Prioritized Technical Recommendations

Priority	Recommendation	Target Component	Rationale & Mitigation Details
P1	Introduce a re‑entrancy guard (checks‑effects‑interactions) on all external calls in `StrategyRouter.rebalance()`. Refactor to update `totalAssets` before external calls or use OpenZeppelin’s `ReentrancyGuard`.	`StrategyRouter`	Eliminates A1. Guarantees that state cannot be double‑counted even if a malicious strategy re‑enters.
P1	Add strict timestamp validation and fallback fallback to a “trusted” feed. Require at least two fresh feeds (≤ 5 min) for median calculation; reject if any feed is stale.	`OracleAggregator`	Mitigates A2 by preventing stale‑price manipulation.
P2	Migrate `Strategist` role to a multi‑signature DAO (e.g., 3‑of‑5 Gnosis Safe). Keep a single “Strategist” address for backward compatibility but require DAO approval for any role change.	`AccessControl` / Governance	Reduces insider risk (A3) and aligns with best‑practice governance.
P2	Implement safe‑fallback logic for `emergencyWithdraw()`. Use a `try/catch` that reverts on failure and does not update `totalAssets` until assets are confirmed returned. Emit an `EmergencyWithdrawFailed` event.	`StrategyRouter`	Prevents accounting divergence (A4).
P2	Add per‑sender monotonic nonce to bridge message verification. Store `lastProcessedNonce[sender]` and require `nonce > lastProcessedNonce`. Include nonce in the Merkle leaf.	L2 Bridge (`MessageVerifier`)	Blocks replay attacks (A5).
P3	Introduce a “price‑impact” check on `deposit()`. Compute expected `pricePerShare` after

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