DestChainConfigV2 to Onramp- PR 287 Audit | Chainlink Labs

Summary

100% of all REPORTED Findings have been addressed

About this report

Assessment Type

Assurance Assessment

Date of Engagement

September 8th, 2025 - September 12th, 2025

Source Code

chainlink-aptos

Assessed Commit ID

f0d729b

Severity Breakdown

0Risk Accepted
5Acknowledged
2Solved
7All Findings

Critical0
High0
Medium0
Low1
- 1Solved
Informational6
- 5Ack.
- 1Solved

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.

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.

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.

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 ( $m_e$ )	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:

$E = \prod m_e$

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 ( $m_I$ )	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:

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

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 ( $C$ )	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:chainlink-aptos

(b) Assessed Commit ID:f0d729b15a030e08e376fb568d70c36dde3f8830

1 files

contracts / ccip / ccip_onramp / sources

1 file

onramp.move

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

2af7d92e7bcb1028c185f9edd56b7977120f688c 072d29094f098d884dd437276dd77cbe2bd1afb6

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

Assessment Summary & Findings Overview#

#	Title	Severity	Score	Status
HAL-01	Post-migration default router_state_address disables sends	Low	2.5	Solved09/22/2025
HAL-02	Unbounded input size in withdraw_fee_tokens can lead to gas-heavy calls	Informational	1.9	Acknowledged09/22/2025
HAL-03	Overly permissive error classes for router authorization failures	Informational	1.3	Solved09/22/2025
HAL-04	No non-zero checks for router/router_state_address on updates	Informational	0.8	Acknowledged09/22/2025
HAL-05	Permissionless fee withdrawal enables griefing/spam and timing manipulation	Informational	0.8	Acknowledged09/22/2025
HAL-06	Allowlist admin can be set to the zero address	Informational	0.3	Acknowledged09/22/2025
HAL-07	Fee withdrawal occurs prior to router/allowlist authorization	Informational	0.0	Acknowledged09/22/2025

Findings & Tech Details#

HAL-01Solved

Post-migration default router_state_address disables sends

Low

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

Description

Recommendation

Remediation Comment

Addressed in:

2af7d92e7bcb1028c185f9edd56b7977120f688c

HAL-02Acknowledged

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

Informational

1.9AO:A/AC:L/AX:M/R:P/S:U/C:N/A:M/I:N/D:L/Y:NAO:A/AC:L/AX:M/R:P/S:U/C:N/A:M/I:N/D:L/Y:N

Description

Recommendation

Remediation Comment

HAL-03Solved

Overly permissive error classes for router authorization failures

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

072d29094f098d884dd437276dd77cbe2bd1afb6

HAL-04Acknowledged

No non-zero checks for router/router_state_address on updates

Informational

0.8AO:S/AC:L/AX:L/R:P/S:U/C:N/A:H/I:N/D:N/Y:NAO:S/AC:L/AX:L/R:P/S:U/C:N/A:H/I:N/D:N/Y:N

Description

Recommendation

Remediation Comment

HAL-05Acknowledged

Permissionless fee withdrawal enables griefing/spam and timing manipulation

Informational

0.8AO:A/AC:M/AX:L/R:P/S:U/C:N/A:N/I:L/D:N/Y:NAO:A/AC:M/AX:L/R:P/S:U/C:N/A:N/I:L/D:N/Y:N

Description

Recommendation

Remediation Comment

HAL-06Acknowledged

Allowlist admin can be set to the zero address

Informational

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

Description

Recommendation

Remediation Comment

HAL-07Acknowledged

Fee withdrawal occurs prior to router/allowlist authorization

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

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.