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DestChainConfigV2 to Onramp- PR 287 - Chainlink Labs

Prepared by:

Halborn Logo

HALBORN

Last Updated 09/25/2025

Date of Engagement: September 8th, 2025 - September 12th, 2025

Summary

100% of all REPORTED Findings have been addressed

All findings

7

Critical

0

High

0

Medium

0

Low

1

Informational

6

Table of Contents

1. Introduction

Chainlink Labs engaged Halborn to conduct a security assessment of several packages for the Aptos blockchain, beginning on September 8th, 2025, and ending on September 12th, 2025. This security assessment focused on the smart contracts within the chainlink-aptos GitHub repository; commit hashes and further details can be found in the Scope section of this report.


The engagement was performed to validate that the V2 migration and configuration changes are upgrade-safe and to identify functional and security issues introduced by the change.

2. Assessment Summary

The team at Halborn assigned one full-time security engineer to verify the security of the smart contracts. The security engineer is a blockchain and smart-contract security expert with advanced penetration testing, smart-contract hacking, and deep knowledge of multiple blockchain protocols.

The purpose of this assessment is to:

    • Ensure that smart contract functions operate as intended.

    • Identify potential security issues with the smart contracts.


In summary, Halborn identified some improvements to reduce the likelihood and impact of risks, which were partially addressed by the Chainlink team. The main ones were the following:

    • Provide explicit router_state_address values as migration inputs for each destination. Alternatively, ensure ccip_send is gated to return a clear "not configured" error until a non-zero, non-state-address value is set.

    • Impose a reasonable upper bound on fee_tokens.length() or provide documented batching guidance and tooling to process withdrawals in smaller chunks.

    • Use error::permission_denied(E_MUST_BE_CALLED_BY_ROUTER) instead of error::invalid_argument(...) for router authorization checks in both V1 and V2 ccip_send.


3. Test Approach and Methodology

Halborn performed a combination of the manual view of the code and automated security testing to balance efficiency, timeliness, practicality, and accuracy regarding the scope of the smart contract assessment. While manual testing is recommended to uncover flaws in logic, process, and implementation, automated testing techniques help enhance the coverage of smart contracts. They 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 the architecture, purpose, and use of the platform.

    • Manual code review and walkthrough.

    • Manual assessment of the critical Move variables and functions in scope to identify any vulnerability classes related to arithmetic or logic.

    • Cross-contract call controls.

    • Logical controls related to the platform architecture.

    • Review unit tests.


4. 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.

4.1 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

4.2 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}

4.3 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

5. SCOPE

REPOSITORY
(a) Repository: chainlink-aptos
(b) Assessed Commit ID: https://github.com/smartcontractkit/chainlink-aptos/pull/287/commits/f0d729b15a030e08e376fb568d70c36dde3f8830
(c) Items in scope:
  • contracts/ccip/ccip_onramp/sources/onramp.move
Out-of-Scope: Third party dependencies and economic attacks.
Remediation Commit ID:
Out-of-Scope: New features/implementations after the remediation commit IDs.

6. Assessment Summary & Findings Overview

Critical

0

High

0

Medium

0

Low

1

Informational

6

Security analysisRisk levelRemediation Date
Post-migration default router_state_address disables sendsLowSolved - 09/22/2025
Unbounded input size in withdraw_fee_tokens can lead to gas-heavy callsInformationalAcknowledged - 09/22/2025
Overly permissive error classes for router authorization failuresInformationalSolved - 09/22/2025
No non-zero checks for router/router_state_address on updatesInformationalAcknowledged - 09/22/2025
Permissionless fee withdrawal enables griefing/spam and timing manipulationInformationalAcknowledged - 09/22/2025
Allowlist admin can be set to the zero addressInformationalAcknowledged - 09/22/2025
Fee withdrawal occurs prior to router/allowlist authorizationInformationalAcknowledged - 09/22/2025

7. Findings & Tech Details

7.1 Post-migration default router_state_address disables sends

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/smartcontractkit/chainlink-aptos/pull/287/commits/2af7d92e7bcb1028c185f9edd56b7977120f688c

7.2 Unbounded input size in withdraw_fee_tokens can lead to gas-heavy calls

//

Informational

Description
BVSS
Recommendation
Remediation Comment

7.3 Overly permissive error classes for router authorization failures

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/smartcontractkit/chainlink-aptos/pull/287/commits/072d29094f098d884dd437276dd77cbe2bd1afb6

7.4 No non-zero checks for router/router_state_address on updates

//

Informational

Description
BVSS
Recommendation
Remediation Comment

7.5 Permissionless fee withdrawal enables griefing/spam and timing manipulation

//

Informational

Description
BVSS
Recommendation
Remediation Comment

7.6 Allowlist admin can be set to the zero address

//

Informational

Description
BVSS
Recommendation
Remediation Comment

7.7 Fee withdrawal occurs prior to router/allowlist authorization

//

Informational

Description
BVSS
Recommendation
Remediation Comment

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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DestChainConfigV2 to Onramp- PR 287

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