- Hacken
- Audits
- vechain-foundation
- [SCA] VeChain | Stargate | May2025
Introduction
We express our gratitude to the Vechain Foundation team for the collaborative engagement that enabled the execution of this Smart Contract Security Assessment.
The VeChain Stargate smart-contracts suite is a key pillar of the upcoming Hayabusa hard fork in VeChain network, supplying the on-chain framework for delegating stake to validator nodes and for managing exist and future rewards.
Document | |
|---|---|
| Name | Smart Contract Code Review and Security Analysis Report for Vechain Foundation |
| Audited By | Stepan Chekhovskoi, Bohdan Hrytsak |
| Approved By | Ataberk Yavuzer, Seher Saylik |
| Website | https://www.vechain.org→ |
| Changelog | 09/06/2025 - Preliminary Report |
| 26/06/2025 - Remediation Report | |
| 22/07/2025 - Final Report | |
| Platform | VeChain |
| Language | Solidity |
| Tags | Liquid Staking, Non-Fungible Token, Staking |
| Methodology | https://hackenio.cc/sc_methodology→ |
Document
- Name
- Smart Contract Code Review and Security Analysis Report for Vechain Foundation
- Audited By
- Stepan Chekhovskoi, Bohdan Hrytsak
- Approved By
- Ataberk Yavuzer, Seher Saylik
- Website
- https://www.vechain.org→
- Changelog
- 09/06/2025 - Preliminary Report
- 26/06/2025 - Remediation Report
- 22/07/2025 - Final Report
- Platform
- VeChain
- Language
- Solidity
- Tags
- Liquid Staking, Non-Fungible Token, Staking
- Methodology
- https://hackenio.cc/sc_methodology→
Review Scope | |
|---|---|
| Initial Repository | https://github.com/vechain/stargate→ |
| Initial Commit | c49487aedc30830feca8f208bd7bdbfa70246c4d |
| Remediation Commit | 86296662f1c7f10f7844fc7bb90e59a84d615fcd |
| Remediation Commit | f14509e12d407f725a7a57b1e6f071cc072d714b |
| Final Repository | https://github.com/vechain/stargate-contracts→ |
| Final Commit | e083f7e8097a16ca2cfed04a507f6d4103ec8063 |
Review Scope
- Initial Repository
- https://github.com/vechain/stargate→
- Initial Commit
- c49487aedc30830feca8f208bd7bdbfa70246c4d
- Remediation Commit
- 86296662f1c7f10f7844fc7bb90e59a84d615fcd
- Remediation Commit
- f14509e12d407f725a7a57b1e6f071cc072d714b
- Final Repository
- https://github.com/vechain/stargate-contracts→
- Final Commit
- e083f7e8097a16ca2cfed04a507f6d4103ec8063
Audit Summary
The system users should acknowledge all the risks summed up in the risks section of the report
Documentation quality
Functional requirements are shared internally.
Project overview is detailed.
Use-cases are provided.
Technical description is provided.
Run instructions are provided.
Technical specification is provided.
The NatSpec documentation is partially inaccurate.
Code quality
The code mostly follows best practices.
The development environment is configured.
Several redundant code patterns were found.
Few TODO comments are identified.
Missing events emit for certain configuration functions (
setVthoRewardPerBlockForAllLevels,setVthoRewardPerBlockForLevel).Partial missing some input validation in critical functions.
Test coverage
Code coverage of the project is 92.9% (branch coverage, without NodeManagementV1 and NodeManagementV2).
Deployment and user interactions are covered with tests.
Some negative and edge cases coverage is missed.
System Overview
The VeChain Stargate is an upgradeable system implementing special NFT Staking contains following contracts
StargateNFT - upgradeable ERC721 with pauseable functionality and governed by role-based access control. It is a continuation of the legacy Token Auction (X-Node and Eco Nodes) collection. This contract allows users to stake VET and receive an NFT in exchange, which represents a betting position. It also supports the claim of VTHO rewards for user stakes generated by the balance of the VET contract by the VeChain energy growth mechanism and the issuance of this reward to users.
Uses
AccessControlUpgradeableto manage roles.Inherit contracts from OpenZeppelin library:
AccessControlUpgradeable: Access control roles base system.ERC721Upgradeable: Core ERC-721 implementation.ERC721EnumerableUpgradeable: ERC-721 enumeration helpers.ERC721PausableUpgradeable: Allows NFT transfers to be disabled while paused.ReentrancyGuardUpgradeable: Helper for prevent reentrant calls to the stake / unstake / migrate / claim functionality.UUPSUpgradeable: Support UUPS proxy mechanism.
Uses the following protocol libraries to implement the main functionality:
Clock: Current block/timestamp/clock mode helper.DataTypes: Data structures.Errors: Custom errors definitions.Levels: Levels management.MintingLogic: Core stake/unstake & migration flow.Settings: Contract-parameter management.Token: Get tokens/users tokens data helper.VetGeneratedVtho: Support dual-token VeChain economic model. Distribution generated VTH0 rewards.
StargateDelegation - upgradeable contract allows user that owns a StargateNFT start delegating, accumulate VTHO rewards with governed by role-based access control.
Uses
AccessControlUpgradeableto manage roles.Inherit contracts from OpenZeppelin library:
AccessControlUpgradeable: Access control roles base system.ReentrancyGuardUpgradeable: Helper for prevent reentrant calls to the delegate / exit delegation / claim functionalities.UUPSUpgradeable: Support UUPS proxy mechanism.
NodeManagementV1 - upgradeable contract to manage node ownership and delegation within the VeBetter DAO ecosystem.
Uses
AccessControlUpgradeableto manage roles.Inherit contracts from OpenZeppelin library:
AccessControlUpgradeable: Provides access control roles base system.UUPSUpgradeable: Provides functionality for support UUPS proxy mechanism.
NodeManagementV2.sol - Update for NodeManagementV1 version, which includes new helper functions to review delegator and node state.
NodeManagementV3.sol - Update for NodeManagementV2 version, which also includes support for StargateNFT node holders.
Privileged roles
StargateNFT
DEFAULT_ADMIN_ROLE:Super admin role that can grant / revoke other roles and manage the overall access control system.
Can configure the addresses of other contracts that are used, such as:
stargateDelegation(Stargate Delegation),legacyNodes(Token Auction),vthoToken(VTH0 token).Can set VTHO rewards generation end timestamp (estimated Hayabusa hard fork in VeChain timestamp).
UPGRADER_ROLE:Can change proxy implementation.
PAUSER_ROLE:Can change the pause state of the contract, to disallow next actions from user during pause:
stake,stakeAndDelegate,migrate,migrateAndDelegate,unstake,claimVetGeneratedVtho.
LEVEL_OPERATOR_ROLE:Can add / update / deactivate / activate the NFT levels (tiers) and their parameters.
MANAGER_ROLE:Can change base URI for token collection metadata.
StargateDelegation
DEFAULT_ADMIN_ROLE:Super admin role that can grant / revoke other roles and manage the overall access control system.
Inherit the permissions of other roles:
Can change current proxy implementation.
Can change the value of the block reward for NFT levels.
Can set the rewards accumulation end block.
UPGRADER_ROLE:Can change proxy implementation.
OPERATOR_ROLE:Can change the value of the block reward for NFT levels.
Can set the rewards accumulation end block.
NodeMaangementV
DEFAULT_ADMIN_ROLE:Super admin role that can grant / revoke other roles and manage the overall access control system.
Can configure the address of VeChain Nodes contract.
UPGRADER_ROLE:Can change proxy implementation.
NodeMaangementV
DEFAULT_ADMIN_ROLE:Super admin role that can grant / revoke other roles and manage the overall access control system.
Can configure the address of VeChain Nodes contract.
UPGRADER_ROLE:Can change proxy implementation.
NodeMaangementV
DEFAULT_ADMIN_ROLE:Super admin role that can grant / revoke other roles and manage the overall access control system.
Can configure the address of VeChain Nodes contract.
Can configure the address of
StargateNFTcontract.
UPGRADER_ROLE:Can change proxy implementation.
Can initialize v3 parameters (
StargateNFTcontract address).
Potential Risks
Single Points of Failure and Control: The project is fully or partially centralized, introducing single points of failure and control. Owner is able to change various parameters including critical configuration which may cause denial of the system. This centralization can lead to vulnerabilities in decision-making and operational processes, making the system more susceptible to targeted attacks or manipulation.
Flexibility and Risk in Contract Upgrades: The project contracts are upgradeable, allowing the administrator to update the contract logic at any time. While this provides flexibility in addressing issues and evolving the project, it also introduces risks if upgrade processes are not properly managed or secured, potentially allowing for unauthorized changes that could compromise the project's integrity and security.
Dynamic Array Iteration Gas Limit Risks: The project iterates over large dynamic arrays, which leads to excessive gas costs, risking denial of service due to out-of-gas errors, directly impacting contract usability and reliability.
Absence of Emergency Withdraw Functionality: The contract is designed in a centralized way leaving all the controls to the system management team. In case of emergency situation, the team is expected to pause the contract and manage the situation. The users are not provided with emergency mechanism to act independently in critical situations.
System Reliance on External Contracts: The functioning of the system relies on Token Auction contract external contract. The contract is responsible for Legacy NFT generation and further creation of Legacy NFTs may cause various system inconsistencies including system DoS requiring contract upgrade. Any flaws or vulnerabilities in these contracts adversely affect the audited project, potentially leading to security breaches or loss of funds.
Findings
Code ― | Title | Status | Severity | |
|---|---|---|---|---|
| F-2025-1084 | Claim Process DoS due to Reentrancy Protection | fixed | High | |
| F-2025-1080 | Estimated VTHO Reward Stop Timestamp May Miss Actual VeChain Network Fork Time | fixed | Medium | |
| F-2025-1065 | Delegation on Behalf of Another User due to Ownership Check Bypass | fixed | Medium | |
| F-2025-1064 | Initializers Could Be Front-Run | accepted | Low | |
| F-2025-1052 | Token URI ERC-721 Metadata Incompliance | fixed | Low | |
| F-2025-1081 | Possible disabling the isActive flag for migrate tiers may cause false expectations | fixed | Low | |
| F-2025-1075 | Inconsistent and Always-True Boolean Return Pattern | fixed | Low | |
| F-2025-1064 | Unexpected Return Values Caused by EIP-150 63/64 Gas-Rule in try/catch | fixed | Low | |
| F-2025-1084 | Unimplemented Scaled Rewards Functionality | accepted | Observation | |
| F-2025-1063 | Lack of Upgradeable Contracts Initialization | fixed | Observation |
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 | |
|---|---|
| Initial Repository | https://github.com/vechain/stargate→ |
| Initial Commit | c49487aedc30830feca8f208bd7bdbfa70246c4d |
| Remediation Commit | 86296662f1c7f10f7844fc7bb90e59a84d615fcd |
| Remediation Commit | f14509e12d407f725a7a57b1e6f071cc072d714b |
| Final Repository | https://github.com/vechain/stargate-contracts→ |
| Final Commit | e083f7e8097a16ca2cfed04a507f6d4103ec8063 |
| Whitepaper | https://www.vechain.org/assets/whitepaper/whitepaper-3-0.pdf→ |
| Requirements | GitBook space shares internally |
| Technical Requirements | README.md |
Scope Details
- Initial Repository
- https://github.com/vechain/stargate→
- Initial Commit
- c49487aedc30830feca8f208bd7bdbfa70246c4d
- Remediation Commit
- 86296662f1c7f10f7844fc7bb90e59a84d615fcd
- Remediation Commit
- f14509e12d407f725a7a57b1e6f071cc072d714b
- Final Repository
- https://github.com/vechain/stargate-contracts→
- Final Commit
- e083f7e8097a16ca2cfed04a507f6d4103ec8063
- Requirements
- GitBook space shares internally
- Technical Requirements
- README.md
Assets in Scope
Appendix 3. Additional Valuables
Verification of System Invariants
During the audit of VeChain / Stargate, Hacken followed its methodology by performing fuzz-testing on the project's main functions. Foundry →, a tool used in the Solidity testing framework, was employed to check how the protocol behaves under various input conditions. Due to the complex and dynamic interactions within the protocol, unexpected edge cases might arise. Therefore, it was important to use invariant 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 Foundry fuzzing suite was prepared for this task, and throughout the assessment, 16 invariants were tested over >16M runs. This thorough testing ensured that the system works correctly even with unexpected or unusual inputs.
Invariant | Test Result | Run Count |
|---|---|---|
| Total NFT token supply must never exceed the sum of all level caps | Passed | 1M |
| X-Level tokens can never be deactivated | Failed | 1M |
| Recorded level (isX & maturityBlocks) parameters must remain immutable | Failed | 1M |
| String contract parameters must be not empty (BaseURI, Name, Symbol) | Failed | 1M |
| Core contract parameters addresses must never be zero | Passed | 1M |
| Circulating supply for each level must stay within its cap | Passed | 1M |
| NFT Total supply must equal the sum of all NFT holder balances | Passed | 1M |
| Every minted token must belong to a valid level | Passed | 1M |
| Total staked VET always eq VET deposited via stake | Passed | 1M |
| NFT Token state match level requirement after mint, during nft live | Failed | 1M |
| Level identifiers must never include zero | Passed | 1M |
| Level identifiers must be in right order without duplicate | Passed | 1M |
| NFT never in both can trasnfer and in delegated state | Passed | 1M |
| Normal NFT count never exceed total supply | Failed | 1M |
| xToken NFT count never exceed total supply | Failed | 1M |
| Sum Normal and xToken equal total supply | Failed | 1M |
Invariant
- Total NFT token supply must never exceed the sum of all level caps
Test Result
- Passed
Run Count
- 1M
Invariant
- X-Level tokens can never be deactivated
Test Result
- Failed
Run Count
- 1M
Invariant
- Recorded level (isX & maturityBlocks) parameters must remain immutable
Test Result
- Failed
Run Count
- 1M
Invariant
- String contract parameters must be not empty (BaseURI, Name, Symbol)
Test Result
- Failed
Run Count
- 1M
Invariant
- Core contract parameters addresses must never be zero
Test Result
- Passed
Run Count
- 1M
Invariant
- Circulating supply for each level must stay within its cap
Test Result
- Passed
Run Count
- 1M
Invariant
- NFT Total supply must equal the sum of all NFT holder balances
Test Result
- Passed
Run Count
- 1M
Invariant
- Every minted token must belong to a valid level
Test Result
- Passed
Run Count
- 1M
Invariant
- Total staked VET always eq VET deposited via stake
Test Result
- Passed
Run Count
- 1M
Invariant
- NFT Token state match level requirement after mint, during nft live
Test Result
- Failed
Run Count
- 1M
Invariant
- Level identifiers must never include zero
Test Result
- Passed
Run Count
- 1M
Invariant
- Level identifiers must be in right order without duplicate
Test Result
- Passed
Run Count
- 1M
Invariant
- NFT never in both can trasnfer and in delegated state
Test Result
- Passed
Run Count
- 1M
Invariant
- Normal NFT count never exceed total supply
Test Result
- Failed
Run Count
- 1M
Invariant
- xToken NFT count never exceed total supply
Test Result
- Failed
Run Count
- 1M
Invariant
- Sum Normal and xToken equal total supply
Test Result
- Failed
Run Count
- 1M
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.