Mae Drop1 Contracts - TAEX

Prepared by:

HALBORN

Last Updated 06/18/2025

Date of Engagement: June 16th, 2025 - June 17th, 2025

Summary

100% of all REPORTED Findings have been addressed

All findings

Critical

High

Medium

Low

Informational

1. Introduction
2. Assessment summary
3. Test approach and methodology
4. Risk methodology
5. Scope
6. Assessment summary & findings overview
7. Findings & Tech Details

7.1 Users are able to go over the maximum allowed mints
7.2 Users could be charged more than expected upon minting
7.3 Cross-chain signature replay possible under specific conditions
7.4 Unnecessary initialization of the current phase
7.5 Unnecessary initialization of an nft's metadata
7.6 Unnecessary payable casts in multiple places
7.7 Floating pragma
7.8 Custom errors should be used
7.9 Consider using named mappings
7.10 Functions that change state don't emit events

1. Introduction

TAEX engaged Halborn to conduct a security assessment on their smart contracts beginning on June 16th, 2025 and ending on June 17th, 2025. The security assessment was scoped to the smart contracts provided to Halborn. Commit hashes and further details can be found in the Scope section of this report.

The Mae Drop1 Contracts codebase in scope consists of a smart contract responsible for supporting an NFT sale through different mint phases such as a whitelist and a public phase.

2. Assessment Summary

Halborn was provided 2 days for the engagement and assigned a full-time security engineer to review the security of the smart contracts in scope.

The purpose of the assessment is to:

Identify potential security issues within the smart contracts.
Ensure that smart contract functionality operates as intended.

In summary, Halborn identified some improvements to reduce the likelihood and impact of risks, which were acknowledged by the TAEX team. The main ones were the following:

Enforce the maximum NFTs per address invariant upon moderator mints.
Consider including the block chain ID in the message hash.
Consider allowing users to provide a slippage upon NFT mints.

3. Test Approach and Methodology

Halborn performed a manual review of the code. Manual testing is great to uncover flaws in logic, process, and implementation.

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

Research into 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 Solidity variables and functions in scope that could led to arithmetic related vulnerabilities.

4. 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) Specific (AO:S)	1 0.2
Attack Cost (AC)	Low (AC:L) Medium (AC:M) High (AC:H)	1 0.67 0.33
Attack Complexity (AX)	Low (AX:L) Medium (AX:M) High (AX:H)	1 0.67 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) Low (C:L) Medium (C:M) High (C:H) Critical (C:C)	0 0.25 0.5 0.75 1
Integrity (I)	None (I:N) Low (I:L) Medium (I:M) High (I:H) Critical (I:C)	0 0.25 0.5 0.75 1
Availability (A)	None (A:N) Low (A:L) Medium (A:M) High (A:H) Critical (A:C)	0 0.25 0.5 0.75 1
Deposit (D)	None (D:N) Low (D:L) Medium (D:M) High (D:H) Critical (D:C)	0 0.25 0.5 0.75 1
Yield (Y)	None (Y:N) Low (Y:L) Medium (Y:M) High (Y:H) Critical (Y:C)	0 0.25 0.5 0.75 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) Partial (R:P) Full (R:F)	1 0.5 0.25
Scope ( $s$ )	Changed (S:C) Unchanged (S:U)	1.25 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.

Severity	Score Value Range
Critical	9 - 10
High	7 - 8.9
Medium	4.5 - 6.9
Low	2 - 4.4
Informational	0 - 1.9

5. SCOPE

REPOSITORY

(a) Repository: mae-drop1-contracts

(b) Assessed Commit ID: d05748f

MAENFTCollection.sol

Out-of-Scope: External dependencies and economic attacks.

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

6. Assessment Summary & Findings Overview

Critical

High

Medium

Low

Informational

Security analysis	Risk level	Remediation Date
Users are able to go over the maximum allowed mints	Medium	Risk Accepted - 06/18/2025
Users could be charged more than expected upon minting	Low	Risk Accepted - 06/18/2025
Cross-chain signature replay possible under specific conditions	Low	Risk Accepted - 06/18/2025
Unnecessary initialization of the current phase	Informational	Acknowledged - 06/18/2025
Unnecessary initialization of an NFT's metadata	Informational	Acknowledged - 06/18/2025
Unnecessary payable casts in multiple places	Informational	Acknowledged - 06/18/2025
Floating pragma	Informational	Acknowledged - 06/18/2025
Custom errors should be used	Informational	Acknowledged - 06/18/2025
Consider Using Named Mappings	Informational	Acknowledged - 06/18/2025
Functions that change state don't emit events	Informational	Acknowledged - 06/18/2025

Remediation Comment

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.

1. Introduction
2. Assessment summary
3. Test approach and methodology
4. Risk methodology
5. Scope
6. Assessment summary & findings overview
7. Findings & Tech Details

7.1 Users are able to go over the maximum allowed mints
7.2 Users could be charged more than expected upon minting
7.3 Cross-chain signature replay possible under specific conditions
7.4 Unnecessary initialization of the current phase
7.5 Unnecessary initialization of an nft's metadata
7.6 Unnecessary payable casts in multiple places
7.7 Floating pragma
7.8 Custom errors should be used
7.9 Consider using named mappings
7.10 Functions that change state don't emit events

// Download the full report

Mae Drop1 Contracts

* Use Google Chrome for best results

** Check "Background Graphics" in the print settings if needed