XBridge Hack

TOTAL LOST $1.9M
Medium Access Control bsc ethereum

Summarize with AI

ChatGPT Perplexity Claude Grok
Affected Chain bsc 2 chains affected
Recovered - No recovery reported
All-Time Rank #658 By amount stolen
Auditors 1 Prior security audit

Incident Overview

Quick Summary

XBridge, a cross-chain platform connecting Ethereum Mainnet and BNB chain, experienced a significant smart contract vulnerability on April 24, 2024. This exploit resulted in a loss of assets totaling approximately $1.9 million. The vulnerability allowed the attacker to seamlessly take away assets from the protocol.

Details of the Exploit

The exploit was rooted in a faulty smart contract implementation due to a lack of regulated access control. The attacker invoked a call to the vulnerable contract's withdrawTokens function, enabling them to extract assets from the protocol. Additionally, a flaw in the listToken function allowed anyone to set themselves as the token owner without verification, facilitating unauthorized access to assets.

Block Data Reference

Exploiter:

https://etherscan.io/address/0x0cfc28d1…e4caa7

Exploiter tx example:

https://etherscan.io/tx/0x903d88a9…109c92

Funds are held by exploiter on two networks:

https://etherscan.io/address/0x0cfc28d1…e4caa7

https://bscscan.com/address/0x0cfc28d1…e4caa7

This is classified as a Access Control Attacks . Compare similar hacks →

Incident Report

Protocol / Project XBridge
Date of Incident
Affected Chain(s) bsc ethereum
Attack Technique Access Control
Classification Infrastructure / Bridge
Primary Source View Post-Mortem #1 View Post-Mortem #2

Protocol Information

Protocol Type Bridge
Smart Contract Language Solidity
Official Website xbridge.tech/
Protocol Twitter/X @XBridge_
Team Anonymous
Source Code Unverified

Market Context at Time of Hack

Token Categories
BNB Chain Ecosystem
Protocol Links

What the Attacker Needed to Succeed

Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.

Technical Knowledge Operational-security tradecraft (phishing, malware, leaked seed phrases, or insider access) to obtain treasury signing authority
Capital Required Minimal capital - only enough to cover gas while draining the compromised accounts
On-Chain Access Valid signing authority over the compromised wallets / multisig signers, allowing direct transfer of funds or stake authorization
Target Reconnaissance Identification of XBridge's high-value treasury accounts and the authority / multisig structure controlling them
Execution Speed Speed to drain the compromised accounts before the team detects the breach and revokes signing authority or freezes the assets
Obfuscation Plan A strategy to launder and move stolen funds - typically through mixers, cross-chain bridges, or decentralized DEX swaps to resist tracing

What Auditors Should Check

Could this have been caught in audit? Likely — with a thorough Access Control audit checklist and test coverage
Audited by Audit Report 1 — still lost $1.9M. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to XBridge, these are the critical security checks that could have prevented this incident (April 2024).

  • Verify all logic paths related to Access Control are guarded by proper access controls and input validation - see the Access Control Attacks attack class for patterns
  • Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs

Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.

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Security Audit History

Related Attack Classes

The technique used in this hack maps to these vulnerability classes in our security curriculum:

See all Access Control Attacks examples →

Access Control Attacks

Proof-of-Concept Exploits

1 PoC available
poc-exploits - xbridge
$ XBridge Logic Flaw

Sources & References

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