Metalayer Contracts Audit | Caldera | Halborn Audit Reports

Summary

100% of all REPORTED Findings have been addressed

About this report

Assessment Type

Assurance Assessment

Date of Engagement

April 7th, 2025 - April 11th, 2025

Source Code

metalayer-fetcher

Assessed Commit ID

720ac48

Severity Breakdown

0Risk Accepted
6Acknowledged
25Solved
31All Findings

Critical0
High0
Medium2
- 2Solved
Low4
- 4Solved
Informational25
- 6Ack.
- 19Solved

Summary#

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.

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.

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).

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)	1
Attack Origin (AO)	Specific (AO:S)	0.2
Attack Cost (AC)	Low (AC:L)	1
	Medium (AC:M)	0.67
	High (AC:H)	0.33
Attack Complexity (AX)	Low (AX:L)	1
	Medium (AX:M)	0.67
	High (AX:H)	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)	0
	Low (C:L)	0.25
	Medium (C:M)	0.5
	High (C:H)	0.75
	Critical (C:C)	1
Integrity (I)	None (I:N)	0
	Low (I:L)	0.25
	Medium (I:M)	0.5
	High (I:H)	0.75
	Critical (I:C)	1
Availability (A)	None (A:N)	0
	Low (A:L)	0.25
	Medium (A:M)	0.5
	High (A:H)	0.75
	Critical (A:C)	1
Deposit (D)	None (D:N)	0
	Low (D:L)	0.25
	Medium (D:M)	0.5
	High (D:H)	0.75
	Critical (D:C)	1
Yield (Y)	None (Y:N)	0
	Low (Y:L)	0.25
	Medium (Y:M)	0.5
	High (Y:H)	0.75
	Critical (Y:C)	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)	1
	Partial (R:P)	0.5
	Full (R:F)	0.25
Scope ( $s$ )	Changed (S:C)	1.25
Scope ( $s$ )	Unchanged (S:U)	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.

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

Scope#

(a) Repository:metalayer-fetcher

(b) Assessed Commit ID:720ac482e1a37f05d0cbf206884f6b84ed55a87e

3 files

contracts / src

3 files

lib

1 file

MetalayerMessage.sol

solidity

MetalayerIsm.sol

solidity

MetalayerRouter.sol

solidity

Out-of-Scope:Third party dependencies and economic attacks.

4a069d504c5ab554f4924562b02ce1211619dced bcb980bba1c1d1cccb010d8f571b8da0e202e096 3474eac45be560d24e528aa2afe309f11bb98eaf e95b0047271b85ee12d22318b35ee93f95495792

Out-of-Scope: New features/implementations after the remediation commit IDs.

Assessment Summary & Findings Overview#

#	Title	Severity	Score	Status
HAL-01	Responses in MetalayerIsm Can Be Overridden	Medium	5.0	Solved04/25/2025
HAL-02	ISMs responsible for verifying a message are unintentionally skipped	Medium	5.0	Solved07/03/2025
HAL-03	Unprotected Privileged Roles	Low	2.5	Solved04/25/2025
HAL-04	Incorrect Version Parsing in the MetalayerMessage Library	Low	2.5	Solved04/25/2025
HAL-05	Quoting function not properly implemented, potentially causing failed messages	Low	2.5	Solved07/03/2025
HAL-06	Insufficient Validation of _metadata Structure in verify()	Low	2.1	Solved04/25/2025
HAL-07	MetalayerRouter Bytecode Size Potentially Too Big	Informational	1.3	Acknowledged04/29/2025
HAL-08	Missing Input Validation	Informational	0.3	Solved04/25/2025
HAL-09	Single-step Ownership Transfer Process	Informational	0.3	Solved04/25/2025
HAL-10	Owner Can Renounce Ownership	Informational	0.3	Solved04/25/2025
HAL-11	Unused Legacy OwnableUpgradeable Inheritance	Informational	0.3	Solved04/25/2025
HAL-12	Deprecated OpenZeppelin Functions in Use	Informational	0.1	Solved04/25/2025
HAL-13	Use of Unlicensed Smart Contract	Informational	0.0	Solved04/25/2025
HAL-14	Unlocked Pragma Compiler	Informational	0.0	Solved04/25/2025
HAL-15	Use of Magic Numbers	Informational	0.0	Acknowledged04/29/2025
HAL-16	Lack of Named Mappings	Informational	0.0	Solved04/25/2025
HAL-17	Use of Revert Strings Instead of Custom Errors	Informational	0.0	Acknowledged04/29/2025
HAL-18	Style Guide Optimizations	Informational	0.0	Solved04/25/2025
HAL-19	Lack of Event Emission	Informational	0.0	Solved04/25/2025
HAL-20	Missing Visibility Attribute	Informational	0.0	Solved04/25/2025
HAL-21	Unused Import	Informational	0.0	Solved04/25/2025
HAL-22	Use Calldata For Function Arguments Not Mutated	Informational	0.0	Solved04/25/2025
HAL-23	NatSpec Improvements	Informational	0.0	Solved04/25/2025
HAL-24	Empty revert() Statement	Informational	0.0	Solved04/25/2025
HAL-25	Local Variable Shadows Named Return	Informational	0.0	Solved04/25/2025
HAL-26	Commented Out Code	Informational	0.0	Solved04/25/2025
HAL-27	Typo in a Comment	Informational	0.0	Acknowledged04/25/2025
HAL-28	Inconsistent Casting	Informational	0.0	Solved04/25/2025
HAL-29	Cache Array Length Outside of Loop	Informational	0.0	Solved04/25/2025
HAL-30	Inconsistent Semantics of block.number Across L2 Networks	Informational	0.0	Acknowledged04/30/2025
HAL-31	Multisig Not Supported by MetalayerIsm	Informational	0.0	Acknowledged04/30/2025

Findings & Tech Details#

HAL-01Solved

Responses in MetalayerIsm Can Be Overridden

Medium

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

Description

Recommendation

Remediation Comment

Addressed in:

4a069d504c5ab554f4924562b02ce1211619dced

HAL-02Solved

ISMs responsible for verifying a message are unintentionally skipped

Medium

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

Description

Recommendation

Remediation Comment

Addressed in:

bcb980bba1c1d1cccb010d8f571b8da0e202e096

HAL-03Solved

Unprotected Privileged Roles

Low

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-04Solved

Incorrect Version Parsing in the MetalayerMessage Library

Low

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-05Solved

Quoting function not properly implemented, potentially causing failed messages

Low

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

Description

Recommendation

Remediation Comment

Addressed in:

e95b0047271b85ee12d22318b35ee93f95495792

HAL-06Solved

Insufficient Validation of _metadata Structure in verify()

Low

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

Description

Recommendation

Remediation Comment

Addressed in:

4a069d504c5ab554f4924562b02ce1211619dced

HAL-07Acknowledged

MetalayerRouter Bytecode Size Potentially Too Big

Informational

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

Description

Recommendation

Remediation Comment

HAL-08Solved

Missing Input Validation

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-09Solved

Single-step Ownership Transfer Process

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

4a069d504c5ab554f4924562b02ce1211619dced

HAL-10Solved

Owner Can Renounce Ownership

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

4a069d504c5ab554f4924562b02ce1211619dced

HAL-11Solved

Unused Legacy OwnableUpgradeable Inheritance

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-12Solved

Deprecated OpenZeppelin Functions in Use

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-13Solved

Use of Unlicensed Smart Contract

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-14Solved

Unlocked Pragma Compiler

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-15Acknowledged

Use of Magic Numbers

Informational

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

Description

Recommendation

Remediation Comment

HAL-16Solved

Lack of Named Mappings

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-17Acknowledged

Use of Revert Strings Instead of Custom Errors

Informational

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

Description

Recommendation

Remediation Comment

HAL-18Solved

Style Guide Optimizations

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-19Solved

Lack of Event Emission

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-20Solved

Missing Visibility Attribute

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-21Solved

Unused Import

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

4a069d504c5ab554f4924562b02ce1211619dced

HAL-22Solved

Use Calldata For Function Arguments Not Mutated

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

4a069d504c5ab554f4924562b02ce1211619dced

HAL-23Solved

NatSpec Improvements

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

4a069d504c5ab554f4924562b02ce1211619dced

HAL-24Solved

Empty revert() Statement

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-25Solved

Local Variable Shadows Named Return

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-26Solved

Commented Out Code

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-27Acknowledged

Typo in a Comment

Informational

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

Description

Recommendation

Remediation Comment

HAL-28Solved

Inconsistent Casting

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-29Solved

Cache Array Length Outside of Loop

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

3474eac45be560d24e528aa2afe309f11bb98eaf

HAL-30Acknowledged

Inconsistent Semantics of block.number Across L2 Networks

Informational

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

Description

Recommendation

References

https://docs.arbitrum.io/build-decentralized-apps/arbitrum-vs-ethereum/block-numbers-and-time

Remediation Comment

HAL-31Acknowledged

Multisig Not Supported by MetalayerIsm

Informational

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

Description

Recommendation

Remediation Comment

9. Automated Testing#

Disclaimer#

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.