How much was lost in the OKX hack?

The OKX hack resulted in $2.4M in losses on December 12, 2023.

What attack technique was used in the OKX exploit?

The OKX exploit utilized Access Control. Understanding this attack vector is critical for smart contract auditors and developers building secure DeFi protocols.

How can developers prevent similar smart contract attacks?

Preventing smart contract hacks requires a combination of secure coding practices, thorough security audits, and understanding common attack vectors like reentrancy, oracle manipulation, and access control flaws. Smart Contract Hacking (SCH) provides hands-on training to help developers and auditors identify and prevent vulnerabilities before deployment.

OKX Hack

TOTAL LOST $2.4M

Medium Dec 12, 2023 Access Control

Affected Chain 2023 Incident surface

Recovered - No recovery reported

All-Time Rank #596 By amount stolen

Protocol Type CEX Target category

Incident Overview

Quick Summary

OKX DEX suffered an access control exploit on Dec 12, 2023, resulting in a loss of 2,390,976 USD worth of assets, including USDT, USDC, and WETH.

Details of the Exploit

OKX DEX, a trading aggregator for cross-chain transactions, experienced an access control exploit on December 12, 2023. The proxy admin owner upgraded the DEX proxy contract to a new implementation contract, which may have led to the compromise of the private key of the OKX DEX. After the upgrade, tokens started being stolen from the platform.

The stolen native ETH was distributed between three addresses, while the rest of the stolen stable coins were bridged to Arbitrum and Avalanche chains via Stargate Bridge. The DEX proxy was removed from OKX's platform's trusted list following the incident. The total loss amounted to 2,390,976 USD worth of assets, including 142,034 USDT, 475,929 USDC, and 799.77 WETH.

Block Data Reference

Attackers Addresses:

https://etherscan.io/address/0xFacf375A…010239

https://etherscan.io/address/0x0519efac…78b8a5

Funds Holders as of Dec 14, 2023:

https://etherscan.io/address/0xfe55502a…20468f

https://etherscan.io/address/0x22a2931c…41b0f0

https://etherscan.io/address/0xa15fe801…78d5ad

Malicious Transactions:

https://etherscan.io/tx/0x7a9c0357…a1db5c

https://etherscan.io/tx/0x78bfe55b…49dcd2

https://etherscan.io/tx/0xf69cf6cc…743236

Stargate Bridging Transactions:

https://etherscan.io/tx/0xd2b424b1…99ed28

https://etherscan.io/tx/0x444fe10b…d9dd8b

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

Incident Report

Protocol / Project OKX

Date of Incident December 12, 2023

Attack Technique Access Control

Classification Exchange (DEX)

Primary Source View Post-Mortem

Protocol Information

Protocol Type CEX

Affected Token OKB

Official Website www.okx.com/web3

Protocol Twitter/X @okxweb3

Team Public / Doxxed

Source Code Verified On-Chain

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 OKX'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

If you're auditing a protocol with similar architecture to OKX, these are the critical security checks that could have prevented this incident (December 2023).

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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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

Sources & References

01
Source 1 https://twitter.com/okxweb3/status/1734794114657657004
02
Web Archive https://archive.ph/H4BRU

Threat Assessment

Severity Level

MEDIUM

Attack Vector Access Control
Root Cause Exchange (DEX)
Year 2023

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