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RLC Multichain Bridge - iExec

Prepared by:

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HALBORN

Last Updated 08/14/2025

Date of Engagement: July 8th, 2025 - July 9th, 2025

Summary

100% of all REPORTED Findings have been addressed

All findings

2

Critical

0

High

0

Medium

0

Low

0

Informational

2

Table of Contents

1. Introduction

iExec engaged Halborn to conduct a security assessment on their smart contracts beginning on July 8th, 2025 and ending on July 9th, 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 RLC Multichain Bridge codebase in scope consists of a few different smart contracts, responsible for bridging tokens across chains, using LayerZero.

2. Assessment Summary

Halborn was provided 2 days for the engagement and assigned a full-time security engineer to review the security of the smart contracts in scope.

 

The purpose of the assessment is to:

    • Identify potential security issues within the smart contracts.

    • Ensure that smart contract functionality operates as intended.


In summary, Halborn did not identify any significant security risks. However, some enhancements were recommended to improve code clarity, consistency, or maintainability. These were partially addressed by the iExec team:

    • Consider using a fixed pragma version.

    • Consider fixing the typographical errors in the codebase.


3. Caveats

After the initial assessment, the iExec team reported a role management issue affecting the IexecLayerZeroBridge file. Halborn performed a post-assessment review at pull request PR77 to verify the fixes, and confirmed that the issue has been addressed.

4. Test Approach and Methodology

Halborn performed a manual review of the code. Manual testing is great to uncover flaws in logic, process, and implementation.

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.


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 (I:N)
Low (I:L)
Medium (I:M)
High (I:H)
Critical (I: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: rlc-multichain
(b) Assessed Commit ID: b5e157f
(c) Items in scope:
  • RLCCrosschainToken.sol
  • RLCLiquidityUnifier.sol
  • DualPausableUpgradeable.sol
↓ Expand ↓
Out-of-Scope: External 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

0

Low

0

Informational

2

Security analysisRisk levelRemediation Date
Floating pragmaInformationalAcknowledged - 08/13/2025
Typographical errorInformationalSolved - 07/15/2025

8. Findings & Tech Details

8.1 Floating pragma

//

Informational

Description

Currently, all of the in-scope contracts have a floating pragma version. This is generally considered a bad practice and instead, a fixed pragma version should be used.

BVSS
Recommendation

Consider using a fixed pragma version.

Remediation Comment

ACKNOWLEDGED: The iExec team made a business decision to acknowledge this finding and not alter the contracts.

8.2 Typographical error

//

Informational

Description

IexecLayerZeroBridge and DualPausableUpgradeable use the word outbount instead of outbound in a few places.

BVSS
Recommendation

Consider fixing the typographical errors.

Remediation Comment

SOLVED: The iExec team solved this finding in the specified commit by following the mentioned recommendation.

Remediation Hash
https://github.com/iExecBlockchainComputing/rlc-multichain/commit/82c8c45f11a8928bb400c7d5059f3e7f7d1c1e0c

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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