Earn V2 Core - Standard Implementation Audit | Blueprint Finance

Summary

100% of all REPORTED Findings have been addressed

About this report

Assessment Type

Assurance Assessment

Date of Engagement

September 3rd, 2025 - September 16th, 2025

Source Code

earn-v2-core

Assessed Commit ID

b1b7cec

Severity Breakdown

6Acknowledged
2Risk Accepted
4Solved
12All Findings

Critical0
High0
Medium0
Low3
- 2Risk A.
- 1Solved
Informational9
- 6Ack.
- 3Solved

Introduction#

Blueprint Finance engaged Halborn to perform a security assessment of their smart contracts from September 3rd, 2025 to September 16th, 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 Blueprint Finance codebase in scope consists of smart contracts implementing a modular, upgradeable ERC4626 vault system with strategy allocation, hooks, role-based access control, and factory-managed proxy deployment.

Assessment Summary#

Halborn was allocated 10 days for this engagement and assigned 1 full-time security engineer to conduct a comprehensive review of the smart contracts within scope. The engineer is an expert 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. These were partially addressed by the Blueprint Finance team. The primary recommendations were:

Integrate the performanceFeeHighWaterMark variable into the performance fee logic.
Require that allocated == 0 before allowing a strategy to be removed, regardless of its status. Remove the exception for Halted status.
Update allocation logic to compare the vault's asset balance before and after the call, and use the actual delta for allocated updates.
Require that a strategy is not present in deallocationOrder before allowing its removal, regardless of its status. Alternatively, automatically remove the strategy from deallocationOrder as part of the removal process to ensure consistency.

Test Approach and Methodology#

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).

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:earn-v2-core

(b) Assessed Commit ID:b1b7cece9b50a554c1c21bfd6ba1b18b5b9169cb

14 files

src

14 files

common

1 file

UpgradeableVault.sol

solidity

factory

2 files

ConcreteFactory.sol

solidity

VaultProxy.sol

solidity

implementation

1 file

ConcreteStandardVaultImpl.sol

solidity

lib

9 files

storage

3 files

ConcreteCachedVaultStateStorageLib.sol

solidity

ConcreteFactoryBaseStorageLib.sol

solidity

Out-of-Scope:Third party dependencies and economic attacks.

4f64163e85945785dc6133e6cb0b172dd814f4d0

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

Assessment Summary & Findings Overview#

#	Title	Severity	Score	Status
HAL-01	Strategy can be removed while still holding allocated funds	Low	2.5	Risk Accepted10/03/2025
HAL-02	Lack of non-zero output checks in deposit and redeem can result in user asset loss	Low	2.5	Solved10/03/2025
HAL-03	Unlimited approval risks in AllocateModule	Low	2.0	Risk Accepted10/03/2025
HAL-04	Unused high-water mark in performance fee calculation	Informational	1.7	Acknowledged09/26/2025
HAL-05	Strategy allocation accounting can be manipulated by strategy contracts	Informational	1.3	Acknowledged10/03/2025
HAL-06	Mismatch in performance fee preview vs accrual and liquidity preview vs execution	Informational	0.6	Acknowledged10/03/2025
HAL-07	Hooks can affect share/asset conversion by altering vault balance	Informational	0.6	Acknowledged10/03/2025
HAL-08	Deallocation order can contain stale, missing, or duplicate strategies	Informational	0.5	Acknowledged10/03/2025
HAL-09	Comment/code mismatch	Informational	0.4	Solved10/03/2025
HAL-10	setDeallocationOrder will revert if more than 255 strategies are passed	Informational	0.0	Solved10/03/2025
HAL-11	Floating pragma	Informational	0.0	Acknowledged10/03/2025
HAL-12	Unused imports	Informational	0.0	Solved10/03/2025

Findings & Tech Details#

HAL-01Risk Accepted

Strategy can be removed while still holding allocated funds

Low

2.5AO:S/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:C/Y:CAO:S/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:C/Y:C

Description

Recommendation

Remediation Comment

HAL-02Solved

Lack of non-zero output checks in deposit and redeem can result in user asset loss

Low

2.5AO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:L/Y:NAO:A/AC:L/AX:L/R:N/S:U/C:N/A:N/I:N/D:L/Y:N

Description

Recommendation

Remediation Comment

Addressed in:

Remediation Comment

Addressed in:

Addressed in:

4f64163e85945785dc6133e6cb0b172dd814f4d0

8. Automated Testing#

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.