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Ripple - Batch - Smart Contract Assessment - Ripple

Prepared by:

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HALBORN

Last Updated 06/27/2025

Date of Engagement: January 31st, 2025 - February 13th, 2025

Summary

100% of all REPORTED Findings have been addressed

All findings

5

Critical

2

High

0

Medium

0

Low

2

Informational

1

Table of Contents

1. Introduction

Ripple engaged Halborn to conduct a security assessment on XRP Ledger (XRPL) feature amendments beginning on Jan 31, 2025 and ending on Feb 13, 2025, focusing on PR #5060. The feature introduces a new transaction type Batch that enables atomic execution of multiple transactions, supporting various modes of operation including all-or-nothing, only-one, until-failure, and independent execution patterns.

2. Assessment Summary

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


The scope of this audit encompasses:

    • The new Batch transaction type and its fields

    • Multi-account transaction signing mechanisms

    • Inner transaction security controls

    • Fee calculation and processing

    • Transaction integrity and atomicity guarantees

3. 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 Batch Transaction feature security assessment. The following phases and tools were used:

    • Research into the architecture, purpose, and use of the Batch Transaction feature through extensive documentation review.

    • Manual code review and walkthrough to identify potential logic issues in transaction processing and security controls.

    • Security control testing for signature verification, fee processing, and atomic execution guarantees.

    • Implementation verification of inner transaction controls and batch mode operations.

    • Trust model validation for both single-account and multi-account transaction scenarios.

    • Documentation analysis covering security considerations and implementation guidelines.

    • Functional testing of transaction processing flows and error handling mechanisms.

    • Edge case testing for complex transaction scenarios and failure modes.

    • Review of error handling and recovery mechanisms.


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 (I:N)
Low (I:L)
Medium (I:M)
High (I:H)
Critical (I: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

Files and Repository
(a) Repository: rippled
(b) Assessed Commit ID: e213b6c
(c) Items in scope:
  • src/xrpld/app/tx/detail/Batch.cpp
  • include/xrpl/protocol/XRPAmount.h
  • include/xrpl/protocol/Batch.h
↓ Expand ↓
Out-of-Scope:
Remediation Commit ID:
Out-of-Scope: New features/implementations after the remediation commit IDs.

6. Assessment Summary & Findings Overview

Critical

2

High

0

Medium

0

Low

2

Informational

1

Impact x Likelihood

HAL-01

HAL-02

HAL-03

HAL-04

HAL-05

Security analysisRisk levelRemediation Date
Fee Manipulation in Batch TransactionCriticalSolved
Unbounded Resource Consumption in Fee CalculationCriticalSolved - 03/10/2025
Missing sequence number enforcement in preflightLowSolved - 03/10/2025
Missing OnBehalfOf Transactions CheckLowFuture Release - 03/10/2025
Integer OverflowInformationalSolved - 03/10/2025

7. Findings & Tech Details

7.1 Fee Manipulation in Batch Transaction

//

Critical

Description

The calculateBaseFee The batch transaction processing function is vulnerable to integer overflow, potentially allowing attackers to bypass transaction fee requirements. There's also a missing check at the end of the function to ensure that the fees cannot be zero.


Proof of Concept
        {
            auto const seq = env.seq(alice);
            env(batch::outer(alice, seq, ripple::STAmount(0), tfAllOrNothing),
                batch::inner(pay(alice, bob, XRP(10)), seq + 1),
                batch::inner(pay(bob, alice, XRP(5)), env.seq(bob)),
                batch::sig(bob),
                ter(tesSUCCESS));
            // Close ledger
            env.close();
        }

to simulate a successful attack chaining integer overflow issue and unbounded loop, add this line at the end of the Batch::calculateBaseFee function 

 XRPAmount const TEST = XRPAmount{1};
 return std::numeric_limits<std::uint64_t>::max() + TEST;

BVSS
Recommendation

Always that Batch::calculateBaseFee should never return zero to defend about such attack that could be introduced through unbounded loops or integer overflows.


Remediation Comment

SOLVED: The fee calculation is now improved, and the issue no longer exists

Remediation Hash
https://github.com/XRPLF/rippled/pull/5060/commits/c2c2d2ebc5421e410e005974e6b404af672fadee

7.2 Unbounded Resource Consumption in Fee Calculation

//

Critical

Description

The calculateBaseFee function contains two unbounded loops that process transaction arrays (sfRawTransactions and sfBatchSigners) without proper size validation. Since this function can be triggered through RPC calls before transaction validation or fee payment, an attacker could craft a transaction with extremely large arrays to cause denial of service through excessive CPU consumption.

Proof of Concept
        {
            auto const seq = env.seq(alice);
            env(batch::outer(alice, seq, ripple::STAmount(30), tfAllOrNothing),
                batch::inner(pay(alice, bob, XRP(10)), seq + 1),
                batch::inner(pay(bob, alice, XRP(5)), env.seq(bob)),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                batch::sig(bob),
                ter(tesSUCCESS));
            // Close ledger
            env.close();
        }

BVSS
Recommendation

Add Early Size Validation before the preflight.



Remediation Comment

SOLVED: The issue was solved, and fixes were introduced in isRawTransactionOkay function and calculateBaseFee as well.

Remediation Hash
https://github.com/XRPLF/rippled/pull/5060/commits/bbc88efaf0d755ddc095e95b3ca14cec7fe45e06

7.3 Missing sequence number enforcement in preflight

//

Low

Description

The Batch::preflight() function performs various validations on inner transactions but does not verify sequence numbers of the transactions. While sequence numbers are checked during the actual transaction application phase, performing this validation earlier in the preflight stage could prevent invalid transactions from proceeding further in the processing pipeline.


BVSS
Recommendation

Add sequence number validation in the Batch::preflight() function.

Remediation Comment

SOLVED: The issue is now solved by using unordered_set to store sequence.

Remediation Hash
https://github.com/XRPLF/rippled/pull/5060/commits/85758f8d14a80874ab984093acf0bbc250fb2b68

7.4 Missing OnBehalfOf Transactions Check

//

Low

Description

The specification document states that "OnBehalfOf will not be allowed on Batch transactions" (Section A.9), but there appears to be no explicit validation in the preflight checks to enforce this restriction.

The lack of validation creates a discrepancy between the intended security model and the actual implementation.

BVSS
Recommendation

Add explicit validation in the preflight checks.

Remediation Comment

FUTURE RELEASE: The Ripple team will solve this finding in a future release.

7.5 Integer Overflow

//

Informational

Description

The XRPAmount class in include/xrpl/protocol/XRPAmount.h implements various arithmetic operations for handling XRP amounts in drops (the smallest unit of XRP). The class uses std::int64_t as its underlying type but performs arithmetic operations without overflow/underflow checks, which could lead to silent failures and incorrect balance/fee calculations.

BVSS
Recommendation

Implement checked arithmetic operations that throw exceptions on overflow/underflow.

Remediation Comment

SOLVED: The Ripple team introduced a set of safe math functions safeAdd, safeSub, safeMul, safeNeg.

Remediation Hash
https://github.com/XRPLF/rippled/pull/5330

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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