Smart Contract Assessment Audit | Oro

Summary

100% of all REPORTED Findings have been addressed

About this report

Assessment Type

Assurance Assessment

Date of Engagement

June 1st, 2026 - June 1st, 2026

Source Code

oro-evm

Assessed Commit ID

fdfc0bf

Severity Breakdown

0Acknowledged
3Risk Accepted
5Solved
8All Findings

Critical0
High0
Medium1
- 1Risk A.
Low2
- 2Risk A.
Informational5
- 5Solved

Summary#

Oro engaged Halborn to conduct a security assessment on their smart contracts beginning on June 1st 2026 and ending on June 1st, 2026. The security assessment was scoped to the smart contracts provided in the oro-ethereum-contracts GitHub repository, provided to the Halborn team. Commit hash and further details can be found in the Scope section of this report.

The reviewed contracts form a centralized revenue-capture pipeline for the ORO protocol. OroToken is a capped, pausable ERC-20 with owner-controlled supply. RevenueRouter receives cross-chain stablecoin revenue and splits it between a treasury and a buyback contract at an admin-configured ratio. OroBuyback swaps received stablecoins into ORO via Uniswap V3. The entire flow is gated behind privileged roles with no permissionless participation, making key management the primary trust surface.

ASSESSMENT SUMMARY#

Halborn was provided with 1 day for this engagement and assigned a full-time security engineer to assess the security of the smart contracts in scope. The assigned engineer possesses deep expertise in blockchain and smart contract security, including hands-on experience with multiple blockchain protocols.

The objective of this assessment is to:

Identify potential security issues within the oro-ethereum-contracts smart contracts.
Ensure that smart contract of oro-ethereum-contracts smart contracts functions operate as intended.

In summary, Halborn identified several areas for improvement to reduce the likelihood and impact of security risks, which were partially addressed by the Oro team. The main recommendations were:

Convert minRouteAmount to a per-token mapping so that each registered asset can have an appropriate threshold matching its decimal precision.
Refund excess ETH to the executor after the relayer call.
Combine revenue routing and buyback execution into a single atomic transaction to eliminate the multi-block pre-positioning window.

TEST APPROACH AND METHODOLOGY#

Halborn performed a combination of manual review of the code and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of the smart contract assessment. While manual testing is recommended to uncover flaws in logic, process, and implementation; automated testing techniques help enhance coverage of smart contracts and can quickly identify items that do not follow security best practices.

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

Research into the architecture and purpose of the oro-ethereum-contracts in-scope contracts.
Manual code review and walkthrough of the oro-ethereum-contracts in-scope contracts.
Manual assessment of critical Solidity variables and functions to identify potential vulnerability classes.
Manual testing using custom scripts.
Static Analysis of security for scoped contract, and imported functions. (Slither).
Local deployment and testing with (Foundry, Remix IDE).

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:oro-evm

(b) Assessed Commit ID:fdfc0bf6313f90e067ecf9ef20b096dcafee0a4e

3 files

contracts

3 files

OroBuyback.sol

solidity

OroToken.sol

solidity

RevenueRouter.sol

solidity

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

b4c6efe1466e02cbd55c93631310320d18a67f7e 853a1098972e5ba1a2b5b808a9dfa4cd9408e2a3

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

Assessment Summary & Findings Overview#

#	Title	Severity	Score	Status
HAL-01	Decimal-Agnostic Route Threshold Enforcement Permanently Disables Dust Guard for Higher-Precision Tokens	Medium	5.0	Risk Accepted06/10/2026
HAL-02	Missing Native ETH Return Path After Relayer Interaction	Low	2.5	Risk Accepted06/10/2026
HAL-03	Observable Buyback Allocation Between Routing and Swap Transactions Enables MEV Pre-Positioning	Low	2.5	Risk Accepted06/10/2026
HAL-04	Shared AddressesUpdated Event Across Separate Setters Obscures Which Address Changed for Off-Chain Monitors	Informational	1.3	Solved06/10/2026
HAL-05	Missing Full-Path Token Uniqueness Validation Allows Cyclic Swap Paths That Waste Pool Fees	Informational	1.0	Solved06/10/2026
HAL-06	Undocumented Mempool Exposure During CREATE2 Deployment Risks Front-Running of Initializer Authority	Informational	0.6	Solved06/10/2026
HAL-07	Missing Zero-Amount Mint Rejection Allows No-Op Transactions That Emit Misleading Supply Events	Informational	0.5	Solved06/10/2026
HAL-08	Absent Zero-Balance Sweep Guard Emits Spurious Transfer and Swept Events Polluting Off-Chain Indexers	Informational	0.5	Solved06/10/2026

b4c6efe1466e02cbd55c93631310320d18a67f7e

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.