Mamo PR - Moonwell

1. Summary

2. Introduction

Moonwell engaged Halborn to conduct a security assessment on their smart contracts beginning on June 18th, 2025 and ending on June 19th, 2025. The security assessment was scoped to the smart contracts provided to Halborn. Commit hash and further details can be found in the Scope section of this report.

The smart contracts under review consisted of StrategyFactory, a Factory contract for creating new strategy instances with configurable parameters, and StrategyMulticall, a contract to allow efficient batch updates and generic multicalls to strategies. Furthermore, the security review also added the upgrade of the SlippagePriceChecker contract to make sure no risks were introduced nor storage collisions.

3. Assessment Summary

Halborn was provided 2 days for the engagement, and assigned one full-time security engineer to review the security of the smart contracts in scope. The engineer is a blockchain and smart contract security expert with advanced penetration testing and smart contract hacking skills, and deep knowledge of multiple blockchain protocols.

The objectives of this assessment were to

• Identify potential security issues within the smart contracts.

• Ensure that smart contract functionality operates as intended.

In summary, Halborn identified some improvements to reduce the likelihood and impact of risks, which were completely addressed by the Moonwell team. The main ones were the following:

• Consider refunding excess funds in genericMulticall() or add a withdraw functionallity.

• Add a reentrancy protection to the genericMulticall() function in StrategyMulticall.

4. Test Approach and Methodology

Halborn performed a combination of manual and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of this assessment. While manual testing is recommended to uncover flaws in logic, process, and implementation; automated testing techniques help enhance coverage of the code and can quickly identify items that do not follow the security best practices. The following phases and associated tools were used during the assessment:

• Research into architecture and purpose.

• Smart contract manual code review and walkthrough.

• Graphing out functionality and contract logic/connectivity/functions (solgraph).

• Manual assessment of use and safety for the critical Solidity variables and functions in scope to identify any arithmetic related vulnerability classes.

• Manual testing by custom scripts.

• Static Analysis of security for scoped contract, and imported functions (slither).

• Testnet deployment (Foundry).

5. Storage collision Assessment

Storage collision study was performed as part of this security review. The original SlippagePriceChecker only used Slot 0 and Slot 1:

forge inspect src/SlippagePriceChecker.sol:SlippagePriceChecker storage 

╭-------------------+---------------------------------------------------------------------------+------+--------+-------+---------------------------------------------------╮
| Name              | Type                                                                      | Slot | Offset | Bytes | Contract                                          |
+===========================================================================================================================================================================+
| tokenOracleData   | mapping(address => struct ISlippagePriceChecker.TokenFeedConfiguration[]) | 0    | 0      | 32    | src/SlippagePriceChecker.sol:SlippagePriceChecker |
|-------------------+---------------------------------------------------------------------------+------+--------+-------+---------------------------------------------------|
| maxTimePriceValid | mapping(address => uint256)                                               | 1    | 0      | 32    | src/SlippagePriceChecker.sol:SlippagePriceChecker |
╰-------------------+---------------------------------------------------------------------------+------+--------+-------+---------------------------------------------------╯

The new SlippagePriceChecker uses Slot 0, Slot 1 and Slot 2:

forge inspect src/SlippagePriceChecker.sol:SlippagePriceChecker storage

╭---------------------+-----------------------------------------------------------------------------------------------+------+--------+-------+---------------------------------------------------╮
| Name                | Type                                                                                          | Slot | Offset | Bytes | Contract                                          |
+=================================================================================================================================================================================================+
| tokenOracleData     | mapping(address => struct ISlippagePriceChecker.TokenFeedConfiguration[])                     | 0    | 0      | 32    | src/SlippagePriceChecker.sol:SlippagePriceChecker |
|---------------------+-----------------------------------------------------------------------------------------------+------+--------+-------+---------------------------------------------------|
| maxTimePriceValid   | mapping(address => uint256)                                                                   | 1    | 0      | 32    | src/SlippagePriceChecker.sol:SlippagePriceChecker |
|---------------------+-----------------------------------------------------------------------------------------------+------+--------+-------+---------------------------------------------------|
| tokenPairOracleData | mapping(address => mapping(address => struct ISlippagePriceChecker.TokenFeedConfiguration[])) | 2    | 0      | 32    | src/SlippagePriceChecker.sol:SlippagePriceChecker |
╰---------------------+-----------------------------------------------------------------------------------------------+------+--------+-------+---------------------------------------------------╯

Therefore, no potential collisions were observed.