Introduction
We express our gratitude to the Cradle team for the collaborative engagement that enabled the execution of this Smart Contract Security Assessment.
VestedAirdrop - is a contract that facilitates token distribution using a vesting mechanism with Merkle tree validation.
Document | |
|---|---|
| Name | Smart Contract Code Review and Security Analysis Report for Cradle |
| Audited By | Olesia Bilenka |
| Approved By | Ataberk Yavuzer |
| Website | https://www.cradle.games/→ |
| Changelog | 28/01/2025 - Preliminary Report |
| 28/01/2025 - Final Report | |
| Platform | Ethereum Mainnet |
| Language | Vyper |
| Tags | Airdrop |
| Methodology | https://hackenio.cc/sc_methodology→ |
Document
- Name
- Smart Contract Code Review and Security Analysis Report for Cradle
- Audited By
- Olesia Bilenka
- Approved By
- Ataberk Yavuzer
- Website
- https://www.cradle.games/→
- Changelog
- 28/01/2025 - Preliminary Report
- 28/01/2025 - Final Report
- Platform
- Ethereum Mainnet
- Language
- Vyper
- Tags
- Airdrop
- Methodology
- https://hackenio.cc/sc_methodology→
Review Scope | |
|---|---|
| Repository | https://gist.github.com/krakovia-evm/9079fa8908a520e75d3a376f8b937b58→ |
| Commit | 9079fa8908a520e75d3a376f8b937b58 |
Review Scope
- Commit
- 9079fa8908a520e75d3a376f8b937b58
Audit Summary
The system users should acknowledge all the risks summed up in the risks section of the report.
Documentation quality
Functional requirements are not provided.
Technical description is not provided.
Code quality
The code mostly follows best practices.
The development environment is not configured.
Test coverage
Code coverage of the project is 0% (branch coverage).
Tests were not provided.
System Overview
VestedAirdrop - is a contract that facilitates token distribution using a vesting mechanism with Merkle tree validation. It enables eligible users to claim tokens based on a vesting schedule, which includes an initial release of 31% (TGE) and linear vesting of the remaining 69% over a specified period. The contract ensures secure token distribution, tracks claimed amounts to prevent over-claiming and allows the owner to update the Merkle root or rescue unclaimed tokens
Privileged roles
The owner of the VestedAirdrop contract can update the Merkle root, and rescue unclaimed tokens.
Potential Risks
Owner's Unrestricted State Modification: The absence of restrictions on state variable modifications by the owner leads to arbitrary changes, affecting contract integrity and user trust, especially during critical operations like minting phases.
Findings
Code ― | Title | Status | Severity | |
|---|---|---|---|---|
| F-2025-8526 | Events Missing Indexed Parameters | fixed | Observation | |
| F-2025-8524 | Missing Zero Address Validation | accepted | Observation |
Identify vulnerabilities in your smart contracts.
Appendix 1. Definitions
Severities
When auditing smart contracts, Hacken is using a risk-based approach that considers Likelihood, Impact, Exploitability and Complexity metrics to evaluate findings and score severities.
Reference on how risk scoring is done is available through the repository in our Github organization:
Severity | Description |
|---|---|
Critical | Critical vulnerabilities are usually straightforward to exploit and can lead to the loss of user funds or contract state manipulation. |
High | High vulnerabilities are usually harder to exploit, requiring specific conditions, or have a more limited scope, but can still lead to the loss of user funds or contract state manipulation. |
Medium | Medium vulnerabilities are usually limited to state manipulations and, in most cases, cannot lead to asset loss. Contradictions and requirements violations. Major deviations from best practices are also in this category. |
Low | Major deviations from best practices or major Gas inefficiency. These issues will not have a significant impact on code execution. |
Severity
- Critical
Description
- Critical vulnerabilities are usually straightforward to exploit and can lead to the loss of user funds or contract state manipulation.
Severity
- High
Description
- High vulnerabilities are usually harder to exploit, requiring specific conditions, or have a more limited scope, but can still lead to the loss of user funds or contract state manipulation.
Severity
- Medium
Description
- Medium vulnerabilities are usually limited to state manipulations and, in most cases, cannot lead to asset loss. Contradictions and requirements violations. Major deviations from best practices are also in this category.
Severity
- Low
Description
- Major deviations from best practices or major Gas inefficiency. These issues will not have a significant impact on code execution.
Potential Risks
The "Potential Risks" section identifies issues that are not direct security vulnerabilities but could still affect the project’s performance, reliability, or user trust. These risks arise from design choices, architectural decisions, or operational practices that, while not immediately exploitable, may lead to problems under certain conditions. Additionally, potential risks can impact the quality of the audit itself, as they may involve external factors or components beyond the scope of the audit, leading to incomplete assessments or oversight of key areas. This section aims to provide a broader perspective on factors that could affect the project's long-term security, functionality, and the comprehensiveness of the audit findings.
Appendix 2. Scope
The scope of the project includes the following smart contracts from the provided repository:
Scope Details | |
|---|---|
| Repository | https://gist.github.com/krakovia-evm/9079fa8908a520e75d3a376f8b937b58→ |
| Commit | 9079fa8908a520e75d3a376f8b937b58 |
| Whitepaper | Not provided |
Scope Details
- Commit
- 9079fa8908a520e75d3a376f8b937b58
- Whitepaper
- Not provided
Assets in Scope
Appendix 3. Additional Valuables
Verification of System Invariants
During the audit of Cradle, Hacken followed its methodology by performing fuzz-testing on the project's main functions. Foundry, a tool used for fuzz-testing, was employed to check how the protocol behaves under various inputs. Due to the complex and dynamic interactions within the protocol, unexpected edge cases might arise. Therefore, it was important to use fuzz-testing to ensure that several system invariants hold true in all situations.
Fuzz-testing allows the input of many random data points into the system, helping to identify issues that regular testing might miss. A specific Echidna fuzzing suite was prepared for this task, and throughout the assessment, 9 invariants were tested over 100,000 runs. This thorough testing ensured that the system works correctly even with unexpected or unusual inputs.
Invariant | Test Result | Run Count |
|---|---|---|
| The claimed_amount of a user must never exceed the total allocated amount for that user. | Passed | 100K+ |
The claimed_amount of a user must increase only when a valid claim is processed. | Passed | 100K+ |
The merkle_root must only be updated by the contract owner. | Passed | 100K+ |
Only the owner can call the rescue_tokens function. | Passed | 100K+ |
The rescue_tokens function must reduce the contract's token balance by the specified amount. | Passed | 100K+ |
The claim function must revert if the proof is invalid. | Passed | 100K+ |
The claim function must revert if the current time is before the vesting_start_time. | Passed | 100K+ |
The vested amount calculation must align with the defined 31% TGE and 69% linear vesting formula. | Passed | 100K+ |
After the vesting_end_time, all tokens must be fully vested and claimable. | Passed | 100K+ |
Invariant
- The claimed_amount of a user must never exceed the total allocated amount for that user.
Test Result
- Passed
Run Count
- 100K+
Invariant
- The
claimed_amountof a user must increase only when a validclaimis processed. Test Result
- Passed
Run Count
- 100K+
Invariant
- The
merkle_rootmust only be updated by the contract owner. Test Result
- Passed
Run Count
- 100K+
Invariant
- Only the owner can call the
rescue_tokensfunction. Test Result
- Passed
Run Count
- 100K+
Invariant
- The
rescue_tokensfunction must reduce the contract's token balance by the specified amount. Test Result
- Passed
Run Count
- 100K+
Invariant
- The
claimfunction must revert if theproofis invalid. Test Result
- Passed
Run Count
- 100K+
Invariant
- The
claimfunction must revert if the current time is before thevesting_start_time. Test Result
- Passed
Run Count
- 100K+
Invariant
- The vested amount calculation must align with the defined
31% TGEand69% linear vestingformula. Test Result
- Passed
Run Count
- 100K+
Invariant
- After the
vesting_end_time, all tokens must be fully vested and claimable. Test Result
- Passed
Run Count
- 100K+
Additional Recommendations
The smart contracts in the scope of this audit could benefit from the introduction of automatic emergency actions for critical activities, such as unauthorized operations like ownership changes or proxy upgrades, as well as unexpected fund manipulations, including large withdrawals or minting events. Adding such mechanisms would enable the protocol to react automatically to unusual activity, ensuring that the contract remains secure and functions as intended.
To improve functionality, these emergency actions could be designed to trigger under specific conditions, such as:
Detecting changes to ownership or critical permissions.
Monitoring large or unexpected transactions and minting events.
Pausing operations when irregularities are identified.
These enhancements would provide an added layer of security, making the contract more robust and better equipped to handle unexpected situations while maintaining smooth operations.