Metalayer Contracts - Caldera

Prepared by:

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

Critical

High

Medium

Low

Informational

1. Summary
2. Introduction
3. Assessment summary
4. Test approach and methodology
5. Risk methodology
6. Scope
7. Assessment summary & findings overview
8. Findings & Tech Details

8.1 Responses in metalayerism can be overridden
8.2 Isms responsible for verifying a message are unintentionally skipped
8.3 Unprotected privileged roles
8.4 Incorrect version parsing in the metalayermessage library
8.5 Quoting function not properly implemented, potentially causing failed messages
8.6 Insufficient validation of _metadata structure in verify()
8.7 Metalayerrouter bytecode size potentially too big
8.8 Missing input validation
8.9 Single-step ownership transfer process
8.10 Owner can renounce ownership
8.11 Unused legacy ownableupgradeable inheritance
8.12 Deprecated openzeppelin functions in use
8.13 Use of unlicensed smart contract
8.14 Unlocked pragma compiler
8.15 Use of magic numbers
8.16 Lack of named mappings
8.17 Use of revert strings instead of custom errors
8.18 Style guide optimizations
8.19 Lack of event emission
8.20 Missing visibility attribute
8.21 Unused import
8.22 Use calldata for function arguments not mutated
8.23 Natspec improvements
8.24 Empty revert() statement
8.25 Local variable shadows named return
8.26 Commented out code
8.27 Typo in a comment
8.28 Inconsistent casting
8.29 Cache array length outside of loop
8.30 Inconsistent semantics of block.number across l2 networks
8.31 Multisig not supported by metalayerism

9. Automated Testing

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 ( $m_e$ )	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

Exploitability

E

is calculated using the following formula:

$E = \prod m_e$

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 ( $m_I$ )	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

Impact

I

is calculated using the following formula:

$I = max(m_I) + \frac{\sum{m_I} - max(m_I)}{4}$

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 ( $C$ )	COEFFICIENT VALUE	NUMERICAL VALUE
Reversibility ( $r$ )	None (R:N) Partial (R:P) Full (R:F)	1 0.5 0.25
Scope ( $s$ )	Changed (S:C) Unchanged (S:U)	1.25 1

Severity Coefficient

C

is obtained by the following product:

$C = rs$

The Vulnerability Severity Score

S

is obtained by:

$S = min(10, EIC * 10)$

The score is rounded up to 1 decimal places.

Severity	Score Value Range
Critical	9 - 10
High	7 - 8.9
Medium	4.5 - 6.9
Low	2 - 4.4
Informational	0 - 1.9

6. SCOPE

REPOSITORY

(a) Repository: metalayer-fetcher

(b) Assessed Commit ID: 720ac48

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

High

Medium

Low

Informational

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

8. Findings & Tech Details

8.1 Responses in MetalayerIsm Can Be Overridden

Medium

Description

BVSS

AO:A/AC:L/AX:M/R:N/S:U/C:N/A:N/I:H/D:N/Y:N (5.0)

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

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:M/D:N/Y:N (5.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/bcb980bba1c1d1cccb010d8f571b8da0e202e096

8.3 Unprotected Privileged Roles

Low

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:L/D:N/Y:N (2.5)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.4 Incorrect Version Parsing in the MetalayerMessage Library

Low

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:L/D:N/Y:N (2.5)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.5 Quoting function not properly implemented, potentially causing failed messages

Low

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:L/I:N/D:N/Y:N (2.5)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/e95b0047271b85ee12d22318b35ee93f95495792

8.6 Insufficient Validation of _metadata Structure in verify()

Low

Description

BVSS

AO:A/AC:L/AX:M/R:N/S:U/C:N/A:L/I:L/D:N/Y:N (2.1)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.7 MetalayerRouter Bytecode Size Potentially Too Big

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:P/S:U/C:N/A:L/I:N/D:N/Y:N (1.3)

Recommendation

Remediation Comment

8.8 Missing Input Validation

Informational

Description

BVSS

AO:S/AC:L/AX:L/R:P/S:U/C:N/A:N/I:L/D:N/Y:N (0.3)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.9 Single-step Ownership Transfer Process

Informational

Description

BVSS

AO:S/AC:L/AX:M/R:N/S:U/C:N/A:L/I:N/D:N/Y:N (0.3)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.10 Owner Can Renounce Ownership

Informational

Description

BVSS

AO:S/AC:L/AX:M/R:N/S:U/C:N/A:L/I:N/D:N/Y:N (0.3)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.11 Unused Legacy OwnableUpgradeable Inheritance

Informational

Description

BVSS

AO:A/AC:H/AX:H/R:N/S:U/C:N/A:N/I:L/D:N/Y:N (0.3)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.12 Deprecated OpenZeppelin Functions in Use

Informational

Description

BVSS

AO:S/AC:H/AX:H/R:N/S:U/C:N/A:N/I:L/D:N/Y:N (0.1)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.13 Use of Unlicensed Smart Contract

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.14 Unlocked Pragma Compiler

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.15 Use of Magic Numbers

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

8.16 Lack of Named Mappings

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.17 Use of Revert Strings Instead of Custom Errors

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

8.18 Style Guide Optimizations

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.19 Lack of Event Emission

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.20 Missing Visibility Attribute

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.21 Unused Import

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.22 Use Calldata For Function Arguments Not Mutated

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.23 NatSpec Improvements

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/4a069d504c5ab554f4924562b02ce1211619dced

8.24 Empty revert() Statement

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.25 Local Variable Shadows Named Return

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.26 Commented Out Code

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.27 Typo in a Comment

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

8.28 Inconsistent Casting

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.29 Cache Array Length Outside of Loop

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

Recommendation

Remediation Comment

Remediation Hash

https://github.com/ConstellationCrypto/metalayer-fetcher/commit/3474eac45be560d24e528aa2afe309f11bb98eaf

8.30 Inconsistent Semantics of block.number Across L2 Networks

Informational

Description

BVSS

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

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

AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:N/Y:N (0.0)

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.

1. Summary
2. Introduction
3. Assessment summary
4. Test approach and methodology
5. Risk methodology
6. Scope
7. Assessment summary & findings overview
8. Findings & Tech Details

8.1 Responses in metalayerism can be overridden
8.2 Isms responsible for verifying a message are unintentionally skipped
8.3 Unprotected privileged roles
8.4 Incorrect version parsing in the metalayermessage library
8.5 Quoting function not properly implemented, potentially causing failed messages
8.6 Insufficient validation of _metadata structure in verify()
8.7 Metalayerrouter bytecode size potentially too big
8.8 Missing input validation
8.9 Single-step ownership transfer process
8.10 Owner can renounce ownership
8.11 Unused legacy ownableupgradeable inheritance
8.12 Deprecated openzeppelin functions in use
8.13 Use of unlicensed smart contract
8.14 Unlocked pragma compiler
8.15 Use of magic numbers
8.16 Lack of named mappings
8.17 Use of revert strings instead of custom errors
8.18 Style guide optimizations
8.19 Lack of event emission
8.20 Missing visibility attribute
8.21 Unused import
8.22 Use calldata for function arguments not mutated
8.23 Natspec improvements
8.24 Empty revert() statement
8.25 Local variable shadows named return
8.26 Commented out code
8.27 Typo in a comment
8.28 Inconsistent casting
8.29 Cache array length outside of loop
8.30 Inconsistent semantics of block.number across l2 networks
8.31 Multisig not supported by metalayerism