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Casper 2.0 - Casper Association

Prepared by:

Halborn Logo

HALBORN

Last Updated 04/17/2025

Date of Engagement: December 23rd, 2024 - March 14th, 2025

Summary

100% of all REPORTED Findings have been addressed

All findings

14

Critical

4

High

0

Medium

1

Low

5

Informational

4

Table of Contents

1. Introduction

Casper Association engaged Halborn to conduct a security assessment of the semi-final version of their reference node for Casper Protocol 2.0, beginning on December 23rd, 2024 and ending on March 14th, 2025. The security assessment was scoped to the repository listed with commit hash, and further details in the Scope section of this report.

Casper is the blockchain platform purpose-built to scale opportunity for everyone. Building toward blockchain’s next frontier, Casper is designed for real-world applications without sacrificing usability, cost, decentralization, or security. It removes the barriers that prevent mainstream blockchain adoption by making blockchain friendly to use, open to the world, and future-proof to support innovations today and tomorrow.

2. Assessment Summary

The team at Halborn assigned one full-time security engineer to verify the security of the Casper Protocol 2.0 release. The security 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 this assessment is to:

    • Ensure that the functionalities of the execution engine and data access layer operate as intended

    • Identify potential security issues with the execution engine and data access layer


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

    • Use the PenalizedAccount variant instead of Payment when determining whether the balance identifier corresponds to a penalty.

    • Review the logic for setting the balance identifier when the transaction is intended for the Casper V2 VM, as the balance identifier should not be penalized.

    • Ensure that addressable entities purses are preserved during each upgrade.

    • Use the payment code instead of the session code when handling custom payments and update the phase for the ClearRefundPurse refund mode to Payment.

    • Eliminate the maximum allowed threshold check during the removal of associated keys.

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 blockchain assessment. While manual testing is recommended to uncover flaws in logic, process, and implementation, automated testing techniques help enhance the coverage of modules. 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 walkthrough.

    • 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.

    • Scanning of Rust files for vulnerabilities (cargo audit).

    • Integration testing using a local testing environment.

    • Deployment to devnet through casper-client and nctl.


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: casper-node
(b) Assessed Commit ID: 18955ae
(c) Items in scope:
  • execution_engine/src/runtime/mod.rs
  • execution_engine/src/runtime/utils.rs
  • execution_engine/src/runtime_context/mod.rs
↓ Expand ↓
Out-of-Scope: Third party dependencies and economic attacks.
Remediation Commit ID:
Out-of-Scope: New features/implementations after the remediation commit IDs.

6. Assessment Summary & Findings Overview

Critical

4

High

0

Medium

1

Low

5

Informational

4

Security analysisRisk levelRemediation Date
Flawed Payment Preprocessing Can Render Valid Transactions Ineligible For Execution, And Vice VersaCriticalSolved - 02/11/2025
Transactions Intended For The V2 Runtime Are Ineligible For ExecutionCriticalSolved - 02/07/2025
Addressable Entities Funds Are Lost Upon Each UpgradeCriticalSolved - 03/12/2025
Transactions Using Custom Payment Will FailCriticalSolved - 01/21/2025
Possibility Of Accounts Being Permanently Linked As Associated KeysMediumSolved - 02/07/2025
Possible Inaccurate Gas ChargesLowSolved - 02/12/2025
Improper Error HandlingLowSolved - 02/07/2025
Incorrect Function NameLowSolved - 02/07/2025
Potential Inaccurate Gas Cost CalculationLowSolved - 02/07/2025
Inconsistent Key Mismatch Issue in Mint and Auction System ContractsLowSolved - 03/11/2025
Unnecessary Mutable BorrowsInformationalSolved - 03/31/2025
Presence Of Typographical ErrorsInformationalSolved - 03/31/2025
Inadequate Variable NamingInformationalSolved - 04/04/2025
Misleading CommentsInformationalSolved - 03/31/2025

7. Findings & Tech Details

7.1 Flawed Payment Preprocessing Can Render Valid Transactions Ineligible For Execution, And Vice Versa

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Critical

Description
Proof of Concept
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/4624660c150a8ffbd969ba45f9ee2654455683c9

7.2 Transactions Intended For The V2 Runtime Are Ineligible For Execution

//

Critical

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/c53b183dd7fc5c2342eb48c52a281abfc65c4f2d

7.3 Addressable Entities Funds Are Lost Upon Each Upgrade

//

Critical

Description
Proof of Concept
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/fa31ea5f586629bf1ddbe1f0ceec00ab210ffd69

7.4 Transactions Using Custom Payment Will Fail

//

Critical

Description
Proof of Concept
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/52af64a58a49925dda05c7f606d29f056b5f1784

7.5 Possibility Of Accounts Being Permanently Linked As Associated Keys

//

Medium

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/6fdaaf49540551d9e3bbe9369da59d92b6161b8c

7.6 Possible Inaccurate Gas Charges

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/1d10fa528cff80067aed51e2f43b119218e3a611

7.7 Improper Error Handling

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/2de01c8bbceb0c0ba8278031327eaba005ddb109

7.8 Incorrect Function Name

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/e354218f910bfcda8ea495cc902e27f8f3f0a87f

7.9 Potential Inaccurate Gas Cost Calculation

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/9ebc3756257b0b6f4f274f95dc3d71217260ab6b

7.10 Inconsistent Key Mismatch Issue in Mint and Auction System Contracts

//

Low

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/6483412e1bdd09fe7d36a18412744cff8800d6a9

7.11 Unnecessary Mutable Borrows

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/a40706e796f188ea5bd7866ac86465d8629922ec

7.12 Presence Of Typographical Errors

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/c765264639d17b84119a59a46c021e0b41121cbf

7.13 Inadequate Variable Naming

//

Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/a27d63a35c100233659c7ee87648696286170058

7.14 Misleading Comments

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Informational

Description
BVSS
Recommendation
Remediation Comment
Remediation Hash
https://github.com/casper-network/casper-node/commit/c765264639d17b84119a59a46c021e0b41121cbf

8. Automated Testing

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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Casper 2.0

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