How much was lost in the Impossible Finance hack?

The Impossible Finance hack resulted in $661K in losses on June 21, 2021.

What attack technique was used in the Impossible Finance exploit?

The Impossible Finance exploit utilized Flash Loan Attack. 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.

Impossible Finance Hack

TOTAL LOST $661K

Low Jun 21, 2021 Flash Loan Attack binance

Affected Chain binance Incident surface

Recovered - No recovery reported

All-Time Rank #936 By amount stolen

Auditors 1 Prior security audit

Incident Overview

The attacker's address:

https://bscscan.com/address/0x8e0d334a…72ef02

The transactions behind the attack:

https://explorer.bitquery.io/bsc/txs/calls?internal=false&contract=0xc7ca5478…aa11e6&method=641ccd83

The attacker:

- borrowed 233.3 BNB of flash loan from PancakeSwap

- swapped 65,140 IF tokens

- created a fake token called AAA (BBB)

https://bscscan.com/token/0x9892dd7a…8dac74

- created LP with the fake token and IF token

- swapped 32,570 IF into 221,898 BUSD and another 32,570 IF into 221,898 BUSD using IF router through the FAKE token LP

- repeated the steps from 3 to 5

- sold 556,384 BUSD for 1,731 BNB, repaid the flash loan.

Stolen funds were bridged into Ethereum mainnet onto this address:

https://etherscan.io/address/0x8e0d334a…72ef02

The further destination is unknown.

There are transactions where the Impossible Finance hacker is transferring BNB tokens, which were used to perform a flash loan into the Impossible Finance deployer's address at:

https://bscscan.com/tx/0x05d962a8…dcb244

https://bscscan.com/tx/0x487403ee…6edbb1

In addition:

- Impossible Finance exploiter into 0x6b3 (849.2 BNB):

https://bscscan.com/tx/0x7104c2c1…235eff

- 0x6b3 into Eleven Finance deployer (849 BNB):

https://bscscan.com/tx/0xb70cb9da…6ee4f1

The further funds' flow as follows:

1. Deployer into Gnosis Safe Proxy:

https://bscscan.com/tx/0x48ccb426…01e644

https://bscscan.com/tx/0x1384c22d…d245ec

2. Gnosis Safe Proxy into 0x22b (1,000 BNB):

https://bscscan.com/tx/0xfdb6fec8…a56c96

2.1 Gnosis Safe Proxy into 0x1Cc (521 BNB):

https://bscscan.com/tx/0x63d7b8fd…412e80 (Still on the balance)

3. 0x22b into 0x736 (900 BNB):

https://bscscan.com/tx/0xdb8860fc…bc4941

3.1 0x736 into Disperse (674.35 BNB):

https://bscscan.com/tx/0xf912b616…08c010

https://bscscan.com/tx/0xe705db37…b57776

3.2 0x736 added liquidity into pair WBNB / IF (225 BNB):

https://bscscan.com/tx/0xedcd98a1…e98833

https://bscscan.com/tx/0x3c8de03c…9b772c

https://bscscan.com/tx/0xb9389fce…864f57

4. 0x22b into 0x1Cc (451 BNB):

https://bscscan.com/tx/0xc2484e4e…0fe5fd

https://bscscan.com/tx/0xf984147f…7298c0

4.1 0x1Cc into Binance How wallet (450.99 BNB):

https://bscscan.com/tx/0xf3cef212…a4ebc3

This is classified as a Flash Loans Attacks . Compare similar hacks →

Incident Report

Protocol / Project Impossible Finance

Date of Incident June 21, 2021

Affected Chain(s) binance

Attack Technique Flash Loan Attack

Classification Other

Primary Source View Post-Mortem #1 View Post-Mortem #2

Protocol Information

Protocol Type Launchpad

Affected Token IF

Official Website impossible.finance/

Protocol Twitter/X @impossiblefi

Team Anonymous

Source Code Unverified

Market Context at Time of Hack

Token Categories

DeFi Ethereum Ecosystem Avalanche Ecosystem Solana Ecosystem Fantom Ecosystem BNB Chain Ecosystem

Protocol Links

GitHub

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 Deep understanding of flash loan attack and Solidity and EVM internals

Capital Required Flash loan capital (borrowed atomically, zero upfront cost)

On-Chain Access Ability to interact with binance smart contracts and deploy a custom exploit contract

Protocol Analysis Identification of the exploitable vulnerability in Impossible Finance's contract logic - root cause: other

Execution Speed Precise transaction ordering and timing to exploit the vulnerability within a single atomic block

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? Yes — skilled auditors routinely flag Flash Loan Attack vulnerabilities in code review

Audited by Zokyo — still lost $661K. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to Impossible Finance, these are the critical security checks that could have prevented this incident (June 2021).

Verify all logic paths related to Flash Loan Attack are guarded by proper access controls and input validation - see the Flash Loans 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

Zokyo 2021-06-14 Report

Related Attack Classes

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

See all Flash Loans Attacks examples →

Flash Loans Attacks

Sources & References

01
Source 1 https://medium.com/impossiblefinance/impossible-finance-v2-swap-…
02
Source 2 https://watchpug.medium.com/impossible-finance-exploit-root-caus…

Threat Assessment

Severity Level

LOW

Attack Vector Flash Loan Attack
Root Cause Other
Year 2021

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