Binance hit by $100 million blockchain bridge hack • TechCrunch

Binance, the world’s largest cryptocurrency exchange, confirmed Thursday that hackers got away with at least $100 million, but that the number could have been significantly more.

The Binance blockchain, also known as BNB Chain and Binance Smart Chain, took the rare step of suspending transactions and money transfers after discovering a vulnerability affecting the BSC Token Hub cross-chain bridge. These bridges are designed to facilitate the transfer of assets from one independent blockchain to another.

The vulnerability in the BSC Token Hub bridge allowed the attacker to forge messages, allowing them to create new BNB tokens. Since the stolen tokens were not pre-existing tokens taken from wallets, no user funds were affected.

In a blog post on Friday, the BNB Chain team said a total of 2 million BNB — worth roughly $568 million — was initially withdrawn by the hacker. But blockchain security company SlowMist says the attacker was only able to take about $110 million because the majority of the stolen tokens, worth about $430 million, could not be transferred after the suspension of the BNB chain.

Binance CEO Changpeng Zhao said in a tweet that the company estimates the impact of the breach at between 100 million and 110 million dollars.

“The problem is contained now. Your money is safe. We apologize for the inconvenience and will provide further updates accordingly,” Zhao said.

When contacted for comment, Binance spokesperson Ismael Garcia declined to comment beyond the blog posted by the BNB Chain team, which states that BNB Chain is now back up and running. The blog post adds that a new on-chain governance mechanism will be introduced on the BNB chain to combat and defend against future possible attacks.

“The flaw itself lies in how Binance Bridge processes the evidence of transactions that send the money from one chain to another,” Adrian Hetman, technical lead of the Triaging Team at Immunefi, a web3 bug bounty program provider, told TechCrunch. “The logic checks the message proof, something a user submits, and proceeds with the payout if the proof is valid.”

“The hacker was able to forge such a message that it tricked the logic of the contract into thinking that the message was actually valid, even though the hacker had no valid claim to the funds. BSC Token Hub then proceeded with the payout as everything was valid,” Hetman said.

Cross-chain bro hacks have become a common occurrence in the past year. In June, a hacker exploited a vulnerability to steal $100 million from Harmony’s Horizon Bridge, and in August, attackers siphoned $190 million worth of crypto from the Nomad cross-chain bridge. So far this year, around $2 billion in cryptocurrency has been stolen in cross-chain bridge hacks, according to blockchain data firm Chainalysis.

Earlier this year, hackers stole $625 million after the attack on Axie Infinity’s Ronin Bridge in March.