$566 000 000 USD

OCTOBER 2022

GLOBAL

BINANCE BRIDGE

DESCRIPTION OF EVENTS

"an attacker stole 2 million BNB (~$566M USD) from the Binance Bridge." "the attack appears to have started at 2:30 PM EST [on October 6th, 2022], with the attacker's wallet receiving two transactions [1, 2], each consisting of 1,000,000 BNB."

 

"there was a bug in the way that the Binance Bridge verified proofs which could have allowed attackers to forge arbitrary messages. Fortunately, the attacker here only forged two messages, but the damage could have been far worse"

 

“The bug itself lies in how Binance Bridge processes the proofs of transactions sending the money from one chain to another,” Adrian Hetman, tech 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 managed to forge such a message that it tricked the logic of the contract into thinking the message was indeed valid, even though the hacker didn’t have valid claims to the funds. BSC Token Hub then proceeded with the payout as everything was valid,” said Hetman.

 

"When hackers exploited a bug in the BSC Token Hub (a cross-chain bridge connecting the BNB Beacon Chain and BNB Chain) which allowed them to extract 2M BNB (~$570M), the entire chain was “paused” before the hacker could make off with his exploits. As a result, the hacker only managed to snag ~127M off chain."

 

"The Binance blockchain, also known as BNB Chain and Binance Smart Chain, took the rare step of suspending transactions and fund 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."

 

"Simply put, Binance “asked” all its validators (real nicely) to temporarily suspend the chain."

 

"That’s easy for Binance to do because Binance is also a highly centralized chain with a total of 25 validators, all of whom were pre-approved by Binance themselves."

 

"Binance acknowledged the security incident at 6:19 PM EST and paused the BNB Smart Chain while they investigated the incident.

 

At 7:51 PM EST, the CEO of Binance tweeted that an exploit was used in the BSC Token Hub to transfer the BNB to the attacker and that they had asked all validators to suspend the Binance Smart Chain."

 

"In a blog post on Friday, the BNB Chain team said that a total of 2 million BNB — worth approximately $568 million — were initially withdrawn by the hacker. But blockchain security company SlowMist says the attacker only managed to take about $110 million because the majority of the stolen tokens, worth about $430 million, couldn’t be transferred following the suspension of the BNB Chain."

 

"Binance chief executive Changpeng Zhao said in a tweet that the company estimates the impact of the breach to be between $100 million and $110 million."

 

"When approached for comment, Binance spokesperson Ismael Garcia declined to comment beyond the blog posted by the BNB Chain team, which says that the 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 fight and defend against future possible attacks."

 

"Moving forward, BNB Chain’s validators said they would hold a series of on-chain governance votes that would decide whether the hacked funds should be frozen, as well as whether a bug bounty reward system should be put in place to prevent future hacks."

 

"The Moran hard fork seeks to amend several issues on the BNB Chain stemming from its $100 million hack last week."

An attacker found a massive hole in the proof validation that Binance was using to validate that payments had been made to their bridge, and was able to extract $566m worth of BNB token. The nodes were shut down after $127m was taken off-chain, and the rest of the money was frozen.

Sources And Further Reading

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