Prepared by:
HALBORN
Last Updated 07/15/2025
Date of Engagement: April 7th, 2025 - April 11th, 2025
100% of all REPORTED Findings have been addressed
All findings
31
Critical
0
High
0
Medium
2
Low
4
Informational
25
Caldera engaged Halborn to conduct a security assessment on their MetalayerRouter smart contracts beginning on April 7th, 2025 and ending on April 11th, 2025. The security assessment was scoped to the smart contracts provided to Halborn. Commit hashes and further details can be found in the Scope section of this report.
The MetalayerRouter is a messaging layer built on top of Hyperlane. It is designed for EVM-compatible chains and offers enhanced functionality such as:
1-to-1 messaging between chains
Predefined finality configurations (e.g., rollup-based, RPC soft confirmations).
n-to-1 cross-chain reads via offchain aggregation and CCIP-compatible delivery.
Package encoding for richer message semantics.
Fallback compatibility with Hyperlane interfaces.
Preset ISMs (Interchain Security Modules) and fee hooks controlled at the protocol level.
Halborn was provided 5 days for the engagement and assigned one full-time security engineer to review the security of the smart contract in scope. The engineer is blockchain and smart contract security expert with advanced penetration testing and smart contract hacking skills, and deep knowledge of multiple blockchain protocols.
The purpose of the assessment is to:
Identify potential security issues within the smart contract.
Ensure that smart contract functionality operates as intended.
In summary, Halborn identified some improvements to reduce the likelihood and impact of risks, which were mostly addressed by the Caldera team. The main one was the following:
Do not allow overriding responses in the MetalayerIsm to avoid unexpected behaviour.
Halborn performed a combination of manual review of the code 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 smart contracts and can quickly identify items that do not follow security best practices.
The following phases and associated tools were used throughout the term of the assessment:
Research into architecture, purpose and use of the platform.
Smart contract manual code review and walkthrough to identify any logic issue.
Thorough assessment of safety and usage of critical Solidity variables and functions in scope that could led to arithmetic related vulnerabilities.
Local testing with custom scripts (Foundry).
Fork testing against main networks (Foundry).
Static analysis of security for scoped contract, and imported functions (Slither).
| EXPLOITABILITY METRIC () | METRIC VALUE | NUMERICAL VALUE |
|---|---|---|
| Attack Origin (AO) | Arbitrary (AO:A) Specific (AO:S) | 1 0.2 |
| Attack Cost (AC) | Low (AC:L) Medium (AC:M) High (AC:H) | 1 0.67 0.33 |
| Attack Complexity (AX) | Low (AX:L) Medium (AX:M) High (AX:H) | 1 0.67 0.33 |
| IMPACT METRIC () | METRIC VALUE | NUMERICAL VALUE |
|---|---|---|
| Confidentiality (C) | None (C:N) Low (C:L) Medium (C:M) High (C:H) Critical (C:C) | 0 0.25 0.5 0.75 1 |
| Integrity (I) | None (I:N) Low (I:L) Medium (I:M) High (I:H) Critical (I:C) | 0 0.25 0.5 0.75 1 |
| Availability (A) | None (A:N) Low (A:L) Medium (A:M) High (A:H) Critical (A:C) | 0 0.25 0.5 0.75 1 |
| Deposit (D) | None (D:N) Low (D:L) Medium (D:M) High (D:H) Critical (D:C) | 0 0.25 0.5 0.75 1 |
| Yield (Y) | None (Y:N) Low (Y:L) Medium (Y:M) High (Y:H) Critical (Y:C) | 0 0.25 0.5 0.75 1 |
| SEVERITY COEFFICIENT () | COEFFICIENT VALUE | NUMERICAL VALUE |
|---|---|---|
| Reversibility () | None (R:N) Partial (R:P) Full (R:F) | 1 0.5 0.25 |
| Scope () | Changed (S:C) Unchanged (S:U) | 1.25 1 |
| Severity | Score Value Range |
|---|---|
| Critical | 9 - 10 |
| High | 7 - 8.9 |
| Medium | 4.5 - 6.9 |
| Low | 2 - 4.4 |
| Informational | 0 - 1.9 |
Critical
0
High
0
Medium
2
Low
4
Informational
25
| Security analysis | Risk level | Remediation Date |
|---|---|---|
| Responses in MetalayerIsm Can Be Overridden | Medium | Solved - 04/25/2025 |
| ISMs responsible for verifying a message are unintentionally skipped | Medium | Solved - 07/03/2025 |
| Unprotected Privileged Roles | Low | Solved - 04/25/2025 |
| Incorrect Version Parsing in the MetalayerMessage Library | Low | Solved - 04/25/2025 |
| Quoting function not properly implemented, potentially causing failed messages | Low | Solved - 07/03/2025 |
| Insufficient Validation of _metadata Structure in verify() | Low | Solved - 04/25/2025 |
| MetalayerRouter Bytecode Size Potentially Too Big | Informational | Acknowledged - 04/29/2025 |
| Missing Input Validation | Informational | Solved - 04/25/2025 |
| Single-step Ownership Transfer Process | Informational | Solved - 04/25/2025 |
| Owner Can Renounce Ownership | Informational | Solved - 04/25/2025 |
| Unused Legacy OwnableUpgradeable Inheritance | Informational | Solved - 04/25/2025 |
| Deprecated OpenZeppelin Functions in Use | Informational | Solved - 04/25/2025 |
| Use of Unlicensed Smart Contract | Informational | Solved - 04/25/2025 |
| Unlocked Pragma Compiler | Informational | Solved - 04/25/2025 |
| Use of Magic Numbers | Informational | Acknowledged - 04/29/2025 |
| Lack of Named Mappings | Informational | Solved - 04/25/2025 |
| Use of Revert Strings Instead of Custom Errors | Informational | Acknowledged - 04/29/2025 |
| Style Guide Optimizations | Informational | Solved - 04/25/2025 |
| Lack of Event Emission | Informational | Solved - 04/25/2025 |
| Missing Visibility Attribute | Informational | Solved - 04/25/2025 |
| Unused Import | Informational | Solved - 04/25/2025 |
| Use Calldata For Function Arguments Not Mutated | Informational | Solved - 04/25/2025 |
| NatSpec Improvements | Informational | Solved - 04/25/2025 |
| Empty revert() Statement | Informational | Solved - 04/25/2025 |
| Local Variable Shadows Named Return | Informational | Solved - 04/25/2025 |
| Commented Out Code | Informational | Solved - 04/25/2025 |
| Typo in a Comment | Informational | Acknowledged - 04/25/2025 |
| Inconsistent Casting | Informational | Solved - 04/25/2025 |
| Cache Array Length Outside of Loop | Informational | Solved - 04/25/2025 |
| Inconsistent Semantics of block.number Across L2 Networks | Informational | Acknowledged - 04/30/2025 |
| Multisig Not Supported by MetalayerIsm | Informational | Acknowledged - 04/30/2025 |
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Halborn strongly recommends conducting a follow-up assessment of the project either within six months or immediately following any material changes to the codebase, whichever comes first. This approach is crucial for maintaining the project’s integrity and addressing potential vulnerabilities introduced by code modifications.
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