Binance Bridge Forged Proof Exploit

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BNB Chain

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.

This is a global/international case not involving a specific country.

About Binance Bridge

"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."

This is a global/international case not involving a specific country.

The background of the exchange platform, service, or individuals involved, as it would have been seen or understood at the time of the events.

Include:

• Known history of when and how the service was started.
• What problems does the company or service claim to solve?
• What marketing materials were used by the firm or business?
• Audits performed, and excerpts that may have been included.
• Business registration documents shown (fake or legitimate).
• How were people recruited to participate?
• Public warnings and announcements prior to the event.

Don't Include:

• Any wording which directly states or implies that the business is/was illegitimate, or that a vulnerability existed.
• Anything that wasn't reasonably knowable at the time of the event.

There could be more than one section here. If the same platform is involved with multiple incidents, then it can be linked to a main article page.

The Reality

This sections is included if a case involved deception or information that was unknown at the time. Examples include:

• When the service was actually started (if different than the "official story").
• Who actually ran a service and their own personal history.
• How the service was structured behind the scenes. (For example, there was no "trading bot".)
• Details of what audits reported and how vulnerabilities were missed during auditing.

What Happened

The specific events of the loss and how it came about. What actually happened to cause the loss and some of the events leading up to it.

Key Event Timeline - Binance Bridge Forged Proof Exploit

Date	Event	Description
October 6th, 2022 5:35:00 PM MDT	Samczson Post	Samczsun posts a technical analysis.

Technical Details

This section includes specific detailed technical analysis of any security breaches which happened. What specific software vulnerabilities contributed to the problem and how were they exploited?

Total Amount Lost

The total amount lost has been estimated at $566,000,000 USD.

How much was lost and how was it calculated? If there are conflicting reports, which are accurate and where does the discrepancy lie?

Immediate Reactions

How did the various parties involved (firm, platform, management, and/or affected individual(s)) deal with the events? Were services shut down? Were announcements made? Were groups formed?

Ultimate Outcome

What was the end result? Was any investigation done? Were any individuals prosecuted? Was there a lawsuit? Was any tracing done?

Total Amount Recovered

The total amount recovered has been estimated at $439,000,000 USD.

What funds were recovered? What funds were reimbursed for those affected users?

Ongoing Developments

What parts of this case are still remaining to be concluded?

Individual Prevention Policies

No specific policies for individual prevention have yet been identified in this case.

For the full list of how to protect your funds as an individual, check our Prevention Policies for Individuals guide.

Platform Prevention Policies

Policies for platforms to take to prevent this situation have not yet been selected in this case.

For the full list of how to protect your funds as a financial service, check our Prevention Policies for Platforms guide.

Regulatory Prevention Policies

No specific regulatory policies have yet been identified in this case.

For the full list of regulatory policies that can prevent loss, check our Prevention Policies for Regulators guide.