Smart Contract Assessment Audit | NUVA

Summary

100% of all REPORTED Findings have been addressed

About this report

Assessment Type

Assurance Assessment

Date of Engagement

July 6th, 2026 - July 7th, 2026

Source Code

nuva-evm-contracts

Assessed Commit ID

e37443e

Severity Breakdown

2Acknowledged
3Risk Accepted
5Solved
10All Findings

Critical0
High0
Medium0
Low6
- 3Solved
- 3Risk A.
Informational4
- 2Ack.
- 2Solved

INTRODUCTION#

Nuva engaged Halborn to perform a security assessment of their smart contracts from July 6th, 2026 to July 7th, 2026. The assessment scope was limited to the smart contracts provided to Halborn. Commit hashes and additional details are available in the Scope section of this report.

The Nuva codebase in scope consists of an upgradeable UUPS gatekeeper contract that manages asynchronous, keeper-driven token deposits and multi-phase withdrawals with optional cross-chain bridging via Circle's CCTP.

ASSESSMENT SUMMARY#

Halborn was allocated 2 days for this engagement and assigned 1 full-time security engineer to conduct a comprehensive review of the smart contracts within scope. The engineer is an expert in blockchain and smart contract security, with advanced skills in penetration testing and smart contract exploitation, as well as extensive knowledge of multiple blockchain protocols.

The objectives of this assessment are to:

Identify potential security vulnerabilities within the smart contracts.
Verify that the smart contract functionality operates as intended.

In summary, Halborn identified several areas for improvement to reduce the likelihood and impact of security risks, which were mostly addressed by the Nuva team. The main recommendations were:

Constrain each privileged power with an on-chain bound rather than relying on role trust alone.
Grant DEFAULT_ADMIN_ROLE to the intended administrator during RemoteVault.initialize().
Override renounceOwnership() to revert, consistent with the other contracts in the project, so that ownership cannot be accidentally or maliciously renounced.

TEST APPROACH AND METHODOLODY#

Halborn conducted a combination of manual code review and automated security testing to balance efficiency, timeliness, practicality, and accuracy within the scope of this assessment. While manual testing is crucial for identifying flaws in logic, processes, and implementation, automated testing enhances coverage of smart contracts and quickly detects deviations from established security best practices.

The following phases and associated tools were employed throughout the term of the assessment:

Research into the platform's architecture, purpose and use.
Manual code review and walkthrough of smart contracts to identify any logical issues.
Comprehensive assessment of the safety and usage of critical Solidity variables and functions within scope that could lead to arithmetic-related vulnerabilities.
Local testing using custom scripts (Foundry).
Fork testing against main networks (Foundry).
Static security analysis of scoped contracts, 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.

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:nuva-evm-contracts

(b) Assessed Commit ID:e37443ebbf6f4827631fad7034e5d5a316ba04c4

1 files

contracts

1 file

RemoteVault.sol

solidity

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

13d03f3486b98581d66a9715595d01ec1fdac960

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

Assessment Summary & Findings Overview#

#	Title	Severity	Score	Status
HAL-01	Centralization risks from unbounded privileged-role authority over funds and safety controls	Low	2.5	Solved07/14/2026
HAL-02	Broken standard role management due to unassigned DEFAULT_ADMIN_ROLE	Low	2.0	Risk Accepted07/14/2026
HAL-03	Irrecoverable administration due to missing renounce overrides	Low	2.0	Solved07/14/2026
HAL-04	Stuck settlement-phase funds due to whenNotPaused on the sole payout path	Low	2.0	Risk Accepted07/21/2026
HAL-05	Depositors have no on-chain recovery when shares are never minted	Low	2.0	Risk Accepted07/21/2026
HAL-06	Misdirected CCTP burns due to missing binding between whitelisted destination and target domain	Low	2.0	Solved07/14/2026
HAL-07	Permanent loss of shares and assets due to fixed undeliverable settlement recipient	Informational	1.6	Acknowledged07/21/2026
HAL-08	Missing rescue function leaves surplus and mistakenly-sent tokens strandable	Informational	1.6	Acknowledged07/21/2026
HAL-09	Escrow and settlement fund commingling due to unvalidated token addresses	Informational	1.3	Solved07/14/2026
HAL-10	Permit signature attempted before bridge-mode validation in depositToBridgeWithPermit	Informational	0.0	Solved07/14/2026

Findings & Tech Details#

HAL-01Solved

Centralization risks from unbounded privileged-role authority over funds and safety controls

Low

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

Description

Recommendation

Remediation Comment

Addressed in:

13d03f3486b98581d66a9715595d01ec1fdac960

HAL-02Risk Accepted

Broken standard role management due to unassigned DEFAULT_ADMIN_ROLE

Low

2.0AO:S/AC:L/AX:L/R:N/S:U/C:N/A:C/I:N/D:N/Y:NAO:S/AC:L/AX:L/R:N/S:U/C:N/A:C/I:N/D:N/Y:N

Description

Recommendation

Remediation Comment

HAL-03Solved

Irrecoverable administration due to missing renounce overrides

Low

2.0AO:S/AC:L/AX:L/R:N/S:U/C:N/A:C/I:N/D:N/Y:NAO:S/AC:L/AX:L/R:N/S:U/C:N/A:C/I:N/D:N/Y:N

Description

Recommendation

Remediation Comment

Addressed in:

13d03f3486b98581d66a9715595d01ec1fdac960

HAL-04Risk Accepted

Stuck settlement-phase funds due to whenNotPaused on the sole payout path

Low

2.0AO:S/AC:L/AX:L/R:N/S:U/C:N/A:C/I:N/D:N/Y:NAO:S/AC:L/AX:L/R:N/S:U/C:N/A:C/I:N/D:N/Y:N

Description

Recommendation

Remediation Comment

HAL-05Risk Accepted

Depositors have no on-chain recovery when shares are never minted

Low

2.0AO:S/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:C/Y:NAO:S/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:C/Y:N

Description

Recommendation

Remediation Comment

HAL-06Solved

Misdirected CCTP burns due to missing binding between whitelisted destination and target domain

Low

2.0AO:S/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:C/Y:NAO:S/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:C/Y:N

Description

Recommendation

Remediation Comment

Addressed in:

13d03f3486b98581d66a9715595d01ec1fdac960

HAL-07Acknowledged

Permanent loss of shares and assets due to fixed undeliverable settlement recipient

Informational

1.6AO:A/AC:L/AX:H/R:N/S:U/C:N/A:N/I:N/D:M/Y:NAO:A/AC:L/AX:H/R:N/S:U/C:N/A:N/I:N/D:M/Y:N

Description

Recommendation

Remediation Comment

HAL-08Acknowledged

Missing rescue function leaves surplus and mistakenly-sent tokens strandable

Informational

1.6AO:A/AC:L/AX:H/R:N/S:U/C:N/A:N/I:N/D:M/Y:NAO:A/AC:L/AX:H/R:N/S:U/C:N/A:N/I:N/D:M/Y:N

Description

Recommendation

Remediation Comment

HAL-09Solved

Escrow and settlement fund commingling due to unvalidated token addresses

Informational

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

Description

Recommendation

Remediation Comment

Addressed in:

13d03f3486b98581d66a9715595d01ec1fdac960

HAL-10Solved

Permit signature attempted before bridge-mode validation in depositToBridgeWithPermit

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:

13d03f3486b98581d66a9715595d01ec1fdac960

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.