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CEP18 - Casper Association

Prepared by:

Halborn Logo

HALBORN

Last Updated 07/21/2025

Date of Engagement: June 23rd, 2025 - July 7th, 2025

Summary

100% of all REPORTED Findings have been addressed

All findings

7

Critical

0

High

0

Medium

0

Low

4

Informational

3

Table of Contents

1. Introduction

Casper engaged Halborn to conduct a security assessment of the CEP18 contract, beginning June 23rd, 2024 and ending July 7th, 2024.


The CEP18 contract is the standard token contract within the Casper ecosystem, and the engagement aimed to verify that the Casper network Conder upgrade did not create security vulnerabilities in the updated contract.

2. Assessment Summary

The team at Halborn assigned a full-time security engineer to verify the security of the smart contract. The security engineer is a blockchain and smart-contract security expert with advanced penetration testing, smart-contract hacking, and deep knowledge of multiple blockchain protocols.

The purpose of this assessment is to:

    • Ensure that smart contract functions operate as intended.

    • Identify potential security issues with the smart contracts.


In summary, Halborn identified some improvements to reduce the likelihood and impact of risks, which were mostly addressed by the Casper team. The main ones were the following: 

    • Support the AddressableEntities feature.

    • Synchronize the SDK with the added entry points.

    • Fix the SDK entry point parameters.

    • Fix the SDK events support.

3. Test Approach and Methodology

Halborn performed a combination of the manual view of the code and automated security testing to balance efficiency, timeliness, practicality, and accuracy regarding 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 the coverage of smart contracts. They 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 architecture, purpose, and use of the platform.

    • Manual code read and walk through.

    • Manual Assessment of use and safety for the critical Rust variables and functions in scope to identify any arithmetic related vulnerability classes.

    • Cross contract call controls.

    • Architecture related logical controls.

    • Test complex scenarios with unit tests.


4. 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 (mem_e)METRIC VALUENUMERICAL VALUE
Attack Origin (AO)Arbitrary (AO:A)
Specific (AO:S)		1
0.2
Attack Cost (AC)Low (AC:L)
Medium (AC:M)
High (AC:H)		1
0.67
0.33
Attack Complexity (AX)Low (AX:L)
Medium (AX:M)
High (AX:H)		1
0.67
0.33
Exploitability EE is calculated using the following formula:

E=∏meE = \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 (mIm_I)METRIC VALUENUMERICAL VALUE
Confidentiality (C)None (C:N)
Low (C:L)
Medium (C:M)
High (C:H)
Critical (C:C)		0
0.25
0.5
0.75
1
Integrity (I)None (I:N)
Low (I:L)
Medium (I:M)
High (I:H)
Critical (I:C)		0
0.25
0.5
0.75
1
Availability (A)None (A:N)
Low (A:L)
Medium (A:M)
High (A:H)
Critical (A:C)		0
0.25
0.5
0.75
1
Deposit (D)None (D:N)
Low (D:L)
Medium (D:M)
High (D:H)
Critical (D:C)		0
0.25
0.5
0.75
1
Yield (Y)None (Y:N)
Low (Y:L)
Medium (Y:M)
High (Y:H)
Critical (Y:C)		0
0.25
0.5
0.75
1
Impact II is calculated using the following formula:

I=max(mI)+∑mI−max(mI)4I = 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 (CC)COEFFICIENT VALUENUMERICAL VALUE
Reversibility (rr)None (R:N)
Partial (R:P)
Full (R:F)		1
0.5
0.25
Scope (ss)Changed (S:C)
Unchanged (S:U)		1.25
1
Severity Coefficient CC is obtained by the following product:

C=rsC = rs

The Vulnerability Severity Score SS is obtained by:

S=min(10,EIC∗10)S = min(10, EIC * 10)

The score is rounded up to 1 decimal places.
SeverityScore Value Range
Critical9 - 10
High7 - 8.9
Medium4.5 - 6.9
Low2 - 4.4
Informational0 - 1.9

5. SCOPE

REPOSITORY
(a) Repository: cep18
(b) Assessed Commit ID: eae0263
(c) Items in scope:
  • cep18/contracts/contract/allowances.rs
  • cep18/contracts/contract/balances.rs
  • cep18/contracts/contract/constants.rs
↓ Expand ↓
Out-of-Scope: Economic attacks and external dependencies.
Remediation Commit ID:
Out-of-Scope: New features/implementations after the remediation commit IDs.

6. Assessment Summary & Findings Overview

Critical

0

High

0

Medium

0

Low

4

Informational

3

Security analysisRisk levelRemediation Date
Addressable entities feature activation leads to total loss of fundsLowRisk Accepted - 07/13/2025
SDK is missing eventsLowSolved - 07/13/2025
Missing ChangeEventsModeParams declaration in SDKLowSolved - 07/13/2025
Deprecated BurnerList argument in ChangeSecurityArgsLowSolved - 07/13/2025
Unreachable caller kinds in get_immediate_callerInformationalSolved - 07/13/2025
Redundant sender recipient checkInformationalAcknowledged - 07/13/2025
Unused ENTRY_POINT_UPGRADE constantInformationalSolved - 07/13/2025

7. Findings & Tech Details

7.1 Addressable entities feature activation leads to total loss of funds

//

Low

Description
Proof of Concept
BVSS
Recommendation
Remediation Comment

7.2 SDK is missing events

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-ecosystem/cep18/pull/172

7.3 Missing ChangeEventsModeParams declaration in SDK

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-ecosystem/cep18/pull/172

7.4 Deprecated BurnerList argument in ChangeSecurityArgs

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-ecosystem/cep18/pull/172

7.5 Unreachable caller kinds in get_immediate_caller

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-ecosystem/cep18/pull/172

7.6 Redundant sender recipient check

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-ecosystem/cep18/pull/172

7.7 Unused ENTRY_POINT_UPGRADE constant

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-ecosystem/cep18/pull/172

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.

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