Noga Fallback Contracts Audit | Tea-Fi

Summary

100% of all REPORTED Findings have been addressed

About this report

Assessment Type

Assurance Assessment

Date of Engagement

October 10th, 2025 - October 20th, 2025

Source Code

noga-fallback-contracts

Assessed Commit ID

3492ba9

Severity Breakdown

0Acknowledged
1Risk Accepted
14Solved
15All Findings

Critical0
High0
Medium3
- 3Solved
Low7
- 1Risk A.
- 6Solved
Informational5
- 5Solved

Introduction#

TeaFi engaged Halborn to conduct a security assessment on their smart contracts beginning on October 10, 2025 and ending on October 20, 2025. The scope of this assessment was limited to the smart contracts provided to the Halborn team. Commit hashes and additional details are documented in the Scope section of this report.

TeaFi's Noga Fallback contract's are a modular smart contract system built on the Diamond Standard (EIP‑2535) for secure, gasless ERC‑20 token swaps and transfers. It features upgradeable facets for admin control, whitelisting, and execution, with strict role-based access and slippage protection. Using Permit2 and other permit standards, relayers can perform authorized actions on behalf of users. The system includes treasury-based fee collection, pausability, emergency withdrawals, and safeguards like whitelisted function selectors and reentrancy protection.

Assessment Summary#

Halborn was provided 7 days for the engagement and assigned 1 full-time security engineer to review the security of the smart contracts in scope. The engineer is a blockchain and smart contract security expert with advanced penetration testing and smart contract hacking skills, and deep knowledge of multiple blockchain protocols.

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 several areas for improvement to reduce both the likelihood and impact of potential risks, which were mostly addressed by the TeaFi team. The primary suggestions included:

Modify LibPermit.makeTokenPermit() to check if the current allowance is already sufficient for the transfer amount.
Extract and validate the amountOutMin from callData to ensure it matches.
Implement pre-execution allowance validation before other operations and nonce consumption.
Measure the actual amount received after transfer and use that for refunds.
Remove the msg.value check inside _validateCall().
Remove the unnecessary BaseFacet inheritance from DiamondCutFacet.

Test Approach and Methodology#

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

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

Research into the architecture, purpose, and use of the platform.
Manual code review and walkthrough of the smart contracts to identify potential logic issues.
Manual testing of all core functions, including createCampaign, claim to validate expected behavior and identify edge-case vulnerabilities.
Local testing to simulate contract interactions and validate functional and security assumptions.
Local deployment and testing with Foundry.

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:noga-fallback-contracts

(b) Assessed Commit ID:3492ba99908394e9abcd5ea773697021a8cd7cd0

13 files

contracts

13 files

libraries

4 files

LibAppStorage.sol

solidity

LibDiamond.sol

solidity

LibPermit.sol

solidity

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

a9c2ff1f242e63f941338aed5a68c66d08c3727f 303830a1dc983f724623013d0f17766f8a2e0daa ab4edb56ef6a2c856e6a7562c7d2e11e6c67aec8 1942d08dee8d2346774aae811b4a53117095d369 201a2d0921b11793d68a88baa58bb2d5aed6f6e2 02464cc3d782f99972872792d09f2d768e0abc41 c288589724c8fc4bbd4cee089a3f631cfc866d34 c5f36485e9cc690b7691dcdd6178f4dc0bd047b2 16a2a910bf537aa47eb6dad7a974eee18a27e1d4 1804bd2c2a0cf1519a0c28163e16a50aa598a1d7 74a059c3296bfe396aa9922397e5a68349ade569 fe8585dd52cd7d9da2da9f5a82d993cf7f34e2d4 836c1b5529656b339f3cf86f5942b77f04a78151 ef54b54ef602c233424de6dff3ad027e91e8be61

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

Assessment Summary & Findings Overview#

#	Title	Severity	Score	Status
HAL-01	Front-Running Permit Signatures Causes Transaction Reversion	Medium	5.0	Solved11/10/2025
HAL-02	Griefing Attack via Zero Allowance Causing Relayer Gas Loss	Medium	5.0	Solved11/10/2025
HAL-03	Fee-on-Transfer Token Handling Causes Refund Failures or User Profit from Contract Balance	Medium	5.0	Solved11/10/2025
HAL-04	Users Can Grief Relayers by Providing Mismatched Slippage Parameters	Low	2.5	Risk Accepted11/11/2025
HAL-05	Unused Admin Parameter in DiamondInit Initialization	Low	2.5	Solved11/10/2025
HAL-06	Redundant permit2 Initialization in Diamond Deployment	Low	2.5	Solved11/10/2025
HAL-07	Lack of Emergency Role or Protocol Pause Check for Emergency Withdrawals	Low	2.5	Solved11/10/2025
HAL-08	Unnecessary BaseFacet Inheritance in DiamondCutFacet	Low	2.5	Solved11/10/2025
HAL-09	Unnecessary msg.value > 0 Check in _validateCall()	Low	2.5	Solved11/10/2025
HAL-10	Missing Interface Registrations in DiamondInit Breaks ERC-165 Compliance	Low	2.5	Solved11/10/2025
HAL-11	EmergencyWithdrawErc20 Emits Token Addresses Even When No Tokens Are Withdrawn	Informational	1.7	Solved11/10/2025
HAL-12	setTreasury() Allows Setting the Same Treasury Address Repeatedly	Informational	1.7	Solved11/10/2025
HAL-13	Gas Inefficiency Due to Late Zero Address Check	Informational	1.7	Solved11/10/2025
HAL-14	Missing unchecked Block in replaceFunctions() Selector Loo	Informational	1.7	Solved11/10/2025
HAL-15	Unused Custom Errors	Informational	1.7	Solved11/10/2025

ef54b54ef602c233424de6dff3ad027e91e8be61

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.