RemoteVault and CustomToken Diff Audit Audit | NUVA

Summary

100% of all REPORTED Findings have been addressed

About this report

Assessment Type

Assurance Assessment

Date of Engagement

October 27th, 2026 - October 28th, 2026

Source Code

nuva-evm-contracts-3f81056-sources.zip

Severity Breakdown

0Risk Accepted
2Acknowledged
2Solved
4All Findings

Critical0
High0
Medium0
Low0
Informational4
- 2Ack.
- 2Solved

INTRODUCTION#

NUVA engaged Halborn to conduct a security assessment on their smart contracts beginning on October 27th, 2026 and ending on October 28th, 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 final remediation commit is ffb3e005bd3dc4ba4456650f748bb01639334c3c (main).

The reviewed contracts are the changes to RemoteVault between v1.6.3 and v1.7.1-pre-audit, and to CustomToken between v1.1.0 and v1.7.1-pre-audit. RemoteVault is an AML-compliant vault that takes asset deposits locally or through Circle CCTP and mints CustomToken shares after off-chain settlement on Provenance. The new version adds a deposit cap that compares the Provenance vault TVL, reported by a ProvenanceVaultOracle, plus pending and recently minted deposits against a keeper-set ceiling. CustomToken moves from a fixed deployment to a UUPS-upgradeable ERC20 with Ownable2Step ownership, owner-managed minters, ERC-2612 permit, and EIP-3009 transfer-with-authorization.

ASSESSMENT SUMMARY#

Halborn was provided with 2 days for this engagement and assigned a full-time security engineer to assess the security of the smart contracts in scope. The assigned engineer possesses deep expertise in blockchain and smart contract security, including hands-on experience with multiple blockchain protocols.

The objective of this assessment is to:

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

In summary, Halborn did not identify any significant security risks. However, some enhancements were recommended to improve the deposit cap and ownership controls, which were addressed or acknowledged by the NUVA team. The main recommendations were:

Make the deposit cap count every committed deposit. Count pending pre-upgrade tickets in pendingDepositTotal, add a keeper path that closes an unminted ticket and subtracts it, and use one global figure for in-flight deposits when several deployments feed the same Provenance vault.
Disable ownership renouncement on CustomToken. Override renounceOwnership() and renounceRole() to revert, as the other owner-administered contracts in the repository do.

The following trust assumptions apply to the reviewed design:

The deposit cap relies on the keeper investing each deposit on Provenance before it calls mint(), and on each oracle snapshot reading Provenance no earlier than it writes the snapshot.
The cap treats the Provenance vault TVL, reported in its USD-pegged underlying, as equal to asset token units after decimal rescaling.
The owner and the keeper are trusted. The keeper sets the deposit cap and prices share issuance off-chain, and depositors rely on the operator to issue shares or make them whole off-chain.

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 the smart contract 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 the architecture and purpose of the in-scope contracts.
Manual code review and walkthrough of the in-scope contracts.
Manual assessment of critical Solidity variables and functions to identify potential vulnerability classes.
Manual testing using custom scripts.
Local deployment and testing with (Hardhat).

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) Submitted File: nuva-evm-contracts-3f81056-sources.zip

(b) Items in scope:

2 files

contracts

2 files

CustomToken.sol

solidity

RemoteVault.sol

solidity

06ee48462fe8032606b3c1a853b80626607ff125 ffb3e005bd3dc4ba4456650f748bb01639334c3c

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

Assessment Summary & Findings Overview#

#	Title	Severity	Score	Status
HAL-01	RemoteVault deposit cap ignores in-flight deposits of other deployments that share the Provenance vault	Informational	1.7	Acknowledged10/28/2026
HAL-02	Ownership renouncement permanently disables CustomToken upgrades and minter management	Informational	1.0	Solved10/28/2026
HAL-03	Pre-upgrade pending deposits are not counted against the RemoteVault deposit cap	Informational	0.8	Acknowledged10/28/2026
HAL-04	Unminted deposit tickets permanently consume RemoteVault deposit cap capacity	Informational	0.2	Solved10/28/2026

Findings & Tech Details#

HAL-01Acknowledged

RemoteVault deposit cap ignores in-flight deposits of other deployments that share the Provenance vault

Informational

1.7AO:A/AC:L/AX:M/R:N/S:U/C:N/I:L/A:N/D:N/Y:NAO:A/AC:L/AX:M/R:N/S:U/C:N/I:L/A:N/D:N/Y:N

Description

Recommendation

Remediation Comment

HAL-02Solved

Ownership renouncement permanently disables CustomToken upgrades and minter management

Informational

1.0AO:S/AC:L/AX:L/R:N/S:U/C:N/I:N/A:M/D:N/Y:NAO:S/AC:L/AX:L/R:N/S:U/C:N/I:N/A:M/D:N/Y:N

Description

Recommendation

Remediation Comment

Addressed in:

06ee48462fe8032606b3c1a853b80626607ff125

HAL-03Acknowledged

Pre-upgrade pending deposits are not counted against the RemoteVault deposit cap

Informational

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

Description

Recommendation

Remediation Comment

HAL-04Solved

Unminted deposit tickets permanently consume RemoteVault deposit cap capacity

Informational

0.2AO:S/AC:L/AX:M/R:P/S:U/C:N/I:N/A:L/D:N/Y:NAO:S/AC:L/AX:M/R:P/S:U/C:N/I:N/A:L/D:N/Y:N

Description

Recommendation

Remediation Comment

Addressed in:

ffb3e005bd3dc4ba4456650f748bb01639334c3c

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.