Incident Overview
On April 1, 2023, a flash loan attack was executed on Allbridge's pool in BSC networks, leading to a loss of around $570K due to a flawed pricing calculation logic.
The attacker obtained a flash loan of $7.5M BUSD from PancakeSwap and swapped $2M BUSD for $2M BSC-USD into the pool. They then moved $5M BUSD into another pool, exchanged it for its BSC-USD equivalent, and converted the $5M BSC-USD to its $BUSD equivalent. The attacker then transferred the funds to Allbridge's bridge contract, resulting in substantial profits.
By switching the pool balance, the liquidity pool balance was destroyed, and the pool's liquidity was reduced to $40,000 in balance BUSD. The attacker used $40,000 of BUSD to exchange $790,000 of BSC-USD from Bridge due to broken logic, and finally leveraged Tornado cash to transfer $570,000 in BUSD to their wallet address.
Exploit tx:
https://bscscan.com/tx/0x7ff1364c…ef8210
Attackers:
https://bscscan.com/address/0x2b3cff12…e3e360
https://bscscan.com/address/0xc578d755…5e3984
Incident Report
Protocol Information
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.
What Auditors Should Check
If you're auditing a protocol with similar architecture to Allbridge Core, these are the critical security checks that could have prevented this incident (April 2023).
- Verify all logic paths related to Flashloan Price Oracle Attack / Flash Loan Attack are guarded by proper access controls and input validation - see the Flash Loans Attacks attack class for patterns
- Audit oracle price feeds for manipulation risks - ensure time-weighted average prices (TWAPs) or multi-source aggregators are used, not spot prices
- 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.
Free TrialFunds Recovery
Recovered
$465K
Net Loss
185249
Security Audit History
- Kudelski Security Report
Post-Incident Timeline
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2023-04-03
1500 BNB were returned by the exploiter.
Related Attack Classes
The technique used in this hack maps to these vulnerability classes in our security curriculum:
Proof-of-Concept Exploits
On-Chain Evidence & References
- Twitter/X Alert https://twitter.com/peckshield/status/1642356701100916736
- Twitter/X Alert https://twitter.com/BeosinAlert/status/1642372700726505473
Sources & References
- 01
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02
Web Archive https://archive.ph/dimAG
- 03
- 04
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