Pierluigi Paganini January 31, 2022

Threat actors stole $80M worth of cryptocurrency from the Qubit DeFi platform by exploiting a flaw in the smart contract code used in an Ethereum bridge.

The DeFi platform Qubit Finance was victim of a cyber heist, threat actors stole around $80 million in cryptocurrency last week. The hack took place at around 5PM ET on the evening of January 27th, the attackers have exploited a flaw in the smart contract code used in an Ethereum bridge.

Qubit provides bridging services allowing its users to transfer funds to different blockchains, this means that that the deposits made in one cryptocurrency can be withdrawn in another. Qubit Finance operates a bridge between Ethereum and the Binance Smart Chain (BSC) network.

“The Qubit protocol was subject to an exploit to our QBridge deposit function” reads the incident report published by the company.

Researchers from blockchain security firm CertiK speculate that the attackers were able to exploit a security flaw in Qubit’s smart contract code that allowed them to invoke the deposit() function with malicious input data yet actually deposited 0 ETH and withdraw almost $80 million in Binance Coin in return.

“At 9:34PM UTC on January 27th, 2022, an attacker began their exploit of Qubit Finance’s Ethereum-BSC bridge. This exploit ended up netting them 77,162 qXETH ($185 million), which they then used to borrow and convert 15,688 wETH ($37.6 million), 767 BTC-B ($28.5 million), approximately $9.5 million in various stablecoins, and ~$5 million in CAKE, BUNNY, and MDX.” read the analysis published by CertiK. “At $80 million TVL (Total Value Lost), this is by far the largest exploit of 2022 to date.”

CertiK analysts highlight the importance bridge services that allow investors to move funds among different blockchains.

The Record reported that attacker’s address was identified and threat actors have yet to launder the stolen funds. Qubit Finance published a Twitter to invite the threat actors to negotiate with the team.

The company is open to offer the attackers the maximum reward possible under their bug bounty program, which is $250,000.

Below is the Incident Timeline

1. Jan-27–2022 09:18:55 PM +UTC: 0.8887725 ETH sent from tornado to attacker account
2. Jan-27–2022 09:34:01 PM +UTC~Jan-27–2022 09:50:41 PM +UTC : Sent 16 deposit tx to QBridge of Ethereum
3. Jan-27–2022 09:36:32 PM +UTC~Jan-27–2022 09:51:02 PM +UTC : Sent 16 voteProposal tx to QBridge contract of BSC by Qubit Relayer
4. A number of xETH tokens were minted by 16 voteProposal tx, and liquidity in Qubit was withdrawn using this as collateral

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Pierluigi Paganini

(SecurityAffairs – hacking, REvil ransomware)

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