Prepared by:
HALBORN
Last Updated 12/22/2025
Date of Engagement: December 11th, 2025 - December 12th, 2025
Summary
100% of all REPORTED Findings have been addressed
All findings
5
Critical
0
High
0
Medium
0
Low
4
Informational
1
Table of Contents
1. INTRODUCTION
ZKPass engaged Halborn to perform a security assessment of their smart contracts starting on December 11th, 2025 and ending on December 12th, 2025. 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 AirdropVault contract manages a secure, upgradeable token-airdrop system using EIP-712 signatures and role-based permissions. Admins can deposit tokens and configure TGE/claim windows, while supervisors authorize user claims through signed messages. The contract enforces strict validation, tracks claimed order IDs, and supports both individual and batch claim execution with pausing and emergency-withdrawal controls.
2. ASSESSMENT SUMMARY
Halborn was allocated 2 days for this engagement and assigned 1 full-time security engineers to conduct a comprehensive review of the smart contracts within scope. The engineers are experts 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 ZKPass team. The main recommendations were:
Implement failure-tolerant batch processing that gracefully handles already-claimed orderIds.Modify depositTokens() to automatically cap at remaining capacity.Add validation to ensure _tgeBlock remains before claimDeadLineBlock.
3. 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).
4. SCOPE
- src/AirdropVault.sol
5. Findings Overview
| Security analysis | Risk level | Remediation |
|---|---|---|
| Griefing Attack on delegateClaim Batch Processing | Low | Risk Accepted - 12/18/2025 |
| Direct Transfer Griefing Attack on depositTokens | Low | Solved - 12/18/2025 |
| Missing Validation in updateTGEBlock Allows Invalid Claim Window | Low | Solved - 12/17/2025 |
| Emergency Withdrawal Allows Premature Token Recovery Before Claim Period Ends | Low | Risk Accepted - 12/17/2025 |
| Floating Pragma | Informational | Solved - 12/17/2025 |
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.
Table of Contents
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Airdrop Contract v2
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