Beosin: Vulnerabilities in the way BSC Token Hub uses to validate IAVL trees allow attackers to forge information

According to the monitoring of the Beosin EagleEye platform, BSC Token Hub was attacked by hackers on October 7. The Beosin security team now analyzes the method as follows: Binance cross-chain bridge BSC Token Hub used a special pre-compiled The contract is used to verify the IAVL tree. However, there is a loophole in this implementation, which may allow an attacker to forge arbitrary messages. 1) The attacker first selects the hash value of a successfully submitted block (specified block: 110217401) 2) Then constructs an attack payload as a leaf node on the verified IAVL tree 3) Adds an arbitrary new leaf to the IAVL tree Node 4) At the same time, add a blank internal node to meet the realization proof 5) Adjust the leaf node added in step 3 so that the calculated root hash is equal to the correct root hash selected in step 1 for successful submission 6) Final construction The withdrawal proof of this specific block (110217401) According to the statistics of the Beosin security team, a total of 143.5 million US dollars of stolen funds were transferred through cross-chains (including loans), and about 7739 million of the stolen funds were transferred through cross-chains. USD 10,000 was transferred to Ethereum through various cross-chains, USD 58.96 million was retained in the FTM chain (including various gUSDT), USD 4 million was in the Arbitrum chain, and USD 1.72 million was in the Avalanche chain Of these, $400,000 in Polygon and $1.1 million in Optimism. Beosin Trace is doing real-time tracing of stolen funds.