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Metalayer Contracts - Caldera

Prepared by:

Halborn Logo

HALBORN

Last Updated 07/15/2025

Date of Engagement: April 7th, 2025 - April 11th, 2025

Summary

100% of all REPORTED Findings have been addressed

All findings

31

Critical

0

High

0

Medium

2

Low

4

Informational

25

Table of Contents

1. Summary

2. Introduction

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.

3. Assessment Summary

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.

4. Test Approach and Methodology

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).


5. RISK METHODOLOGY

Every vulnerability and issue observed by Halborn is ranked based on two sets of Metrics and a Severity Coefficient. This system is inspired by the industry standard Common Vulnerability Scoring System.
The two Metric sets are: Exploitability and Impact. Exploitability captures the ease and technical means by which vulnerabilities can be exploited and Impact describes the consequences of a successful exploit.
The Severity Coefficients is designed to further refine the accuracy of the ranking with two factors: Reversibility and Scope. These capture the impact of the vulnerability on the environment as well as the number of users and smart contracts affected.
The final score is a value between 0-10 rounded up to 1 decimal place and 10 corresponding to the highest security risk. This provides an objective and accurate rating of the severity of security vulnerabilities in smart contracts.
The system is designed to assist in identifying and prioritizing vulnerabilities based on their level of risk to address the most critical issues in a timely manner.

5.1 EXPLOITABILITY

Attack Origin (AO):
Captures whether the attack requires compromising a specific account.
Attack Cost (AC):
Captures the cost of exploiting the vulnerability incurred by the attacker relative to sending a single transaction on the relevant blockchain. Includes but is not limited to financial and computational cost.
Attack Complexity (AX):
Describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability. Includes but is not limited to macro situation, available third-party liquidity and regulatory challenges.
Metrics:
EXPLOITABILITY METRIC (mem_e)METRIC VALUENUMERICAL 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
Exploitability EE is calculated using the following formula:

E=∏meE = \prod m_e

5.2 IMPACT

Confidentiality (C):
Measures the impact to the confidentiality of the information resources managed by the contract due to a successfully exploited vulnerability. Confidentiality refers to limiting access to authorized users only.
Integrity (I):
Measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of data stored and/or processed on-chain. Integrity impact directly affecting Deposit or Yield records is excluded.
Availability (A):
Measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. This metric refers to smart contract features and functionality, not state. Availability impact directly affecting Deposit or Yield is excluded.
Deposit (D):
Measures the impact to the deposits made to the contract by either users or owners.
Yield (Y):
Measures the impact to the yield generated by the contract for either users or owners.
Metrics:
IMPACT METRIC (mIm_I)METRIC VALUENUMERICAL 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
Impact II is calculated using the following formula:

I=max(mI)+∑mI−max(mI)4I = max(m_I) + \frac{\sum{m_I} - max(m_I)}{4}

5.3 SEVERITY COEFFICIENT

Reversibility (R):
Describes the share of the exploited vulnerability effects that can be reversed. For upgradeable contracts, assume the contract private key is available.
Scope (S):
Captures whether a vulnerability in one vulnerable contract impacts resources in other contracts.
Metrics:
SEVERITY COEFFICIENT (CC)COEFFICIENT VALUENUMERICAL VALUE
Reversibility (rr)None (R:N)
Partial (R:P)
Full (R:F)		1
0.5
0.25
Scope (ss)Changed (S:C)
Unchanged (S:U)		1.25
1
Severity Coefficient CC is obtained by the following product:

C=rsC = rs

The Vulnerability Severity Score SS is obtained by:

S=min(10,EIC∗10)S = min(10, EIC * 10)

The score is rounded up to 1 decimal places.
SeverityScore Value Range
Critical9 - 10
High7 - 8.9
Medium4.5 - 6.9
Low2 - 4.4
Informational0 - 1.9

6. SCOPE

REPOSITORY
(a) Repository: metalayer-fetcher
(b) Assessed Commit ID: 720ac48
(c) Items in scope:
  • contracts/src/lib/MetalayerMessage.sol
  • contracts/src/MetalayerIsm.sol
  • contracts/src/MetalayerRouter.sol
Out-of-Scope: Third party dependencies and economic attacks.
Remediation Commit ID:
Out-of-Scope: New features/implementations after the remediation commit IDs.

7. Assessment Summary & Findings Overview

Critical

0

High

0

Medium

2

Low

4

Informational

25

Security analysisRisk levelRemediation Date
Responses in MetalayerIsm Can Be OverriddenMediumSolved - 04/25/2025
ISMs responsible for verifying a message are unintentionally skippedMediumSolved - 07/03/2025
Unprotected Privileged RolesLowSolved - 04/25/2025
Incorrect Version Parsing in the MetalayerMessage LibraryLowSolved - 04/25/2025
Quoting function not properly implemented, potentially causing failed messagesLowSolved - 07/03/2025
Insufficient Validation of _metadata Structure in verify()LowSolved - 04/25/2025
MetalayerRouter Bytecode Size Potentially Too BigInformationalAcknowledged - 04/29/2025
Missing Input ValidationInformationalSolved - 04/25/2025
Single-step Ownership Transfer ProcessInformationalSolved - 04/25/2025
Owner Can Renounce OwnershipInformationalSolved - 04/25/2025
Unused Legacy OwnableUpgradeable InheritanceInformationalSolved - 04/25/2025
Deprecated OpenZeppelin Functions in UseInformationalSolved - 04/25/2025
Use of Unlicensed Smart ContractInformationalSolved - 04/25/2025
Unlocked Pragma CompilerInformationalSolved - 04/25/2025
Use of Magic NumbersInformationalAcknowledged - 04/29/2025
Lack of Named MappingsInformationalSolved - 04/25/2025
Use of Revert Strings Instead of Custom ErrorsInformationalAcknowledged - 04/29/2025
Style Guide OptimizationsInformationalSolved - 04/25/2025
Lack of Event EmissionInformationalSolved - 04/25/2025
Missing Visibility AttributeInformationalSolved - 04/25/2025
Unused ImportInformationalSolved - 04/25/2025
Use Calldata For Function Arguments Not MutatedInformationalSolved - 04/25/2025
NatSpec ImprovementsInformationalSolved - 04/25/2025
Empty revert() StatementInformationalSolved - 04/25/2025
Local Variable Shadows Named ReturnInformationalSolved - 04/25/2025
Commented Out CodeInformationalSolved - 04/25/2025
Typo in a CommentInformationalAcknowledged - 04/25/2025
Inconsistent CastingInformationalSolved - 04/25/2025
Cache Array Length Outside of LoopInformationalSolved - 04/25/2025
Inconsistent Semantics of block.number Across L2 NetworksInformationalAcknowledged - 04/30/2025
Multisig Not Supported by MetalayerIsmInformationalAcknowledged - 04/30/2025

8. Findings & Tech Details

8.1 Responses in MetalayerIsm Can Be Overridden

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Medium

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.2 ISMs responsible for verifying a message are unintentionally skipped

//

Medium

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/bcb980bba1c1d1cccb010d8f571b8da0e202e096

8.3 Unprotected Privileged Roles

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.4 Incorrect Version Parsing in the MetalayerMessage Library

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Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.5 Quoting function not properly implemented, potentially causing failed messages

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Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/e95b0047271b85ee12d22318b35ee93f95495792

8.6 Insufficient Validation of _metadata Structure in verify()

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Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.7 MetalayerRouter Bytecode Size Potentially Too Big

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Informational

Description
BVSS
Recommendation
Remediation Comment

8.8 Missing Input Validation

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.9 Single-step Ownership Transfer Process

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.10 Owner Can Renounce Ownership

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.11 Unused Legacy OwnableUpgradeable Inheritance

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.12 Deprecated OpenZeppelin Functions in Use

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.13 Use of Unlicensed Smart Contract

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.14 Unlocked Pragma Compiler

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.15 Use of Magic Numbers

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Informational

Description
BVSS
Recommendation
Remediation Comment

8.16 Lack of Named Mappings

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.17 Use of Revert Strings Instead of Custom Errors

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Informational

Description
BVSS
Recommendation
Remediation Comment

8.18 Style Guide Optimizations

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.19 Lack of Event Emission

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.20 Missing Visibility Attribute

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.21 Unused Import

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.22 Use Calldata For Function Arguments Not Mutated

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.23 NatSpec Improvements

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.24 Empty revert() Statement

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.25 Local Variable Shadows Named Return

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.26 Commented Out Code

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.27 Typo in a Comment

//

Informational

Description
BVSS
Recommendation
Remediation Comment

8.28 Inconsistent Casting

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.29 Cache Array Length Outside of Loop

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.30 Inconsistent Semantics of block.number Across L2 Networks

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Informational

Description
BVSS
Recommendation
Remediation Comment
References
https://docs.arbitrum.io/build-decentralized-apps/arbitrum-vs-ethereum/block-numbers-and-time

8.31 Multisig Not Supported by MetalayerIsm

//

Informational

Description
BVSS
Recommendation
Remediation Comment

9. Automated Testing

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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