Horizen Migration - Code Review Audit | The Horizen Foundation

Summary

100% of all REPORTED Findings have been addressed

About this report

Assessment Type

Assurance Assessment

Date of Engagement

June 11th, 2025 - June 13th, 2025

Source Code

horizen-migration horizen-migration-check

Assessed Commit ID

https://github.com/HorizenOfficial/horizen-migration/tree/1.3.0-RC1 https://github.com/HorizenOfficial/horizen-migration-check/tree/1.3.0

Severity Breakdown

0Risk Accepted
5Acknowledged
2Solved
7All Findings

Critical0
High0
Medium0
Low0
Informational7
- 5Ack.
- 2Solved

Introduction#

The Horizen Foundation engaged Halborn to conduct a security assessment on their smart contracts on June 11th, 2025 to June 13th, 2025. The security assessment was scoped to the smart contracts and scripts provided to the Halborn team.

The Horizen Foundation prepared a migration from all funds of the ZEND and EON blockchains to an ERC20 smart contract on the BASE blockchain and the reviewed scope provided balances dump scripts as well as the BASE smart contracts used to load and claim the migrated balances.

SUMMARY#

The team at Halborn was provided 3 days for the engagement and assigned a security engineer to evaluate the security of the smart contract. 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 the assessment is to:

Ensure that smart contract and scripts functions operate as intended.
Identify potential security issues with the smart contracts or scripts.

In summary, Halborn identified some minor improvements to reduce the likelihood and impact of risks, which have been completely addressed by the Horizen Foundation team. The main ones were the following:

Implement two step ownership transfer process.
Catch signature bad formats before reverting with a generic error.

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, 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 Move variables and functions in scope that could lead to arithmetic related vulnerabilities.
Manual testing by custom scripts.

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:horizen-migration

(b) Assessed Commit ID:https://github.com/HorizenOfficial/horizen-migration/tree/1.3.0-RC1

8 files

dump-scripts / python / horizen_dump_scripts

2 files

setup_eon2_json.py

python

zend_to_horizen.py

python

erc20-migration / contracts

6 files

EONBackupVault.sol

solidity

LinearTokenVesting.sol

solidity

VerificationLibrary.sol

solidity

ZendBackupVault.sol

solidity

ZenMigrationFactory.sol

solidity

ZenToken.sol

solidity

Out-of-Scope:Economic attacks and external dependencies.

(a) Repository:horizen-migration-check

(b) Assessed Commit ID:https://github.com/HorizenOfficial/horizen-migration-check/tree/1.3.0

1 files

check.js

javascript

Out-of-Scope:Economic attacks and external dependencies.

b5d2a80a5f4652dd77e58cd3687ffd79831bc32c

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

Assessment Summary & Findings Overview#

#	Title	Severity	Score	Status
HAL-01	EON Dump Allows Silent Address Re-use	Informational	1.7	Acknowledged06/12/2025
HAL-02	No Two-Step Ownership Transfer	Informational	1.0	Acknowledged06/13/2025
HAL-03	Locked Unclaimed Stake In Vaults	Informational	0.0	Acknowledged06/13/2025
HAL-04	Unnecessary Satoshi-Level Rounding	Informational	0.0	Acknowledged06/13/2025
HAL-05	Unsorted eon_vault_results Array Used	Informational	0.0	Acknowledged06/13/2025
HAL-06	Signature Zero r And s Not Explicitly Rejected	Informational	0.0	Solved06/13/2025
HAL-07	Signature v-Byte Range Not Asserted	Informational	0.0	Solved06/13/2025

Remediation Comment

Addressed in:

b5d2a80a5f4652dd77e58cd3687ffd79831bc32c

HAL-07Solved

Signature v-Byte Range Not Asserted

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:

b5d2a80a5f4652dd77e58cd3687ffd79831bc32c

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.