Slow Fog: UwU Lend Hacked Analysis
Analysis of UwU Lend Being HackedAuthor: Doris, @SlowMist Security Team
Background
On June 10, 2024, according to the MistEye security monitoring system, the platform UwU Lend, which provides digital asset lending services on the EVM chain, was attacked, resulting in a loss of approximately $19.3 million. The SlowMist security team conducted an analysis of the incident and shares the results as follows:
( https :// x . com / SlowMist _ Team / status /1800181916857155761)
Relevant Information
Attacker address:
0x841ddf093f5188989fa1524e7b893de64b421f47
Vulnerable contract address:
0x9bc6333081266e55d88942e277fc809b485698b9
Attack transactions:
0xca1bbf3b320662c89232006f1ec6624b56242850f07e0f1dadbe4f69ba0d6ac3
0xb3f067618ce54bc26a960b660fc28f9ea0315e2e9a1a855ede508eb4017376
0x242a0fb4fde9de0dc2fd42e8db743cbc197fa2bf6a036ba0bba303df296408b
Core of the Attack
The core of this attack lies in the fact that the attacker could manipulate the price oracle directly by making large exchanges in the CurveFinance pool, affecting the price of the sUSDE token, and profiting from the manipulated price by extracting other assets from the pool.
Attack Process
1. Flash loan to drive down the price of USDE: The attacker first borrowed a large amount of assets through a flash loan and exchanged part of the borrowed USDE tokens for other tokens in the Curve pool that could influence the sUSDE price.
2. Create a large number of lending positions: With the current sharp drop in sUSDE price, the attacker borrowed a large amount of sUSDE tokens by depositing other underlying tokens.
3. Manipulate the oracle to raise the price of sUSDE: By performing reverse exchange operations in the previous Curve pool, the price of sUSDE was quickly raised.
4. Liquidate debt positions in large amounts: Due to the rapid increase in the price of sUSDE, the attacker could liquidate a large number of previously borrowed positions to obtain uWETH.
5. Deposit remaining sUSDE and borrow other underlying tokens in the contract: The attacker deposited the currently high-priced sUSDE again to borrow more underlying asset tokens for profit.
It is evident that the attacker mainly profited by repeatedly manipulating the price of sUSDE, borrowing large amounts at low prices, and liquidating and re-mortgaging at high prices. We followed up on the oracle contract sUSDePriceProviderBUniCatch that calculates the sUSDE price:
It can be seen that the price of sUSDE is determined by obtaining different prices for 11 USDE tokens from the CurveFinance USDE pool and the UNI V3 pool, and then sorting these prices and calculating the median.
In the calculation logic here, 5 of the USDE prices are directly obtained using the get_p function to fetch the real-time spot price from the Curve pool, which allowed the attacker to directly influence the median price calculation result through large exchanges in a single transaction.
MistTrack Analysis
According to the on-chain tracking tool MistTrack, the attacker 0x841ddf093f5188989fa1524e7b893de64b421f47 profited approximately $19.3 million in this attack, including assets such as ETH, crvUSD, bLUSD, and USDC, which were subsequently converted to ETH.
By tracing the transaction fees of the attacker's address, it was found that the initial funds in this address came from a Tornado Cash transfer of 0.98 ETH, and the address subsequently received 5 transfers from Tornado Cash.
Expanding the transaction graph reveals that the attacker transferred 1,292.98 ETH to the address 0x48d7c1dd4214b41eda3301bca434348f8d1c5eb6, which currently has a balance of 1,282.98 ETH; the attacker transferred the remaining 4,000 ETH to the address 0x050c7e9c62bf991841827f37745ddadb563feb70, which currently has a balance of 4,010 ETH.
MistTrack has blacklisted the relevant addresses and will continue to monitor the transfer dynamics of the stolen funds.
Conclusion
The core of this attack lies in the attacker exploiting the compatibility flaws in directly obtaining real-time prices from the price oracle and calculating the median price to manipulate the price of sUSDE, thereby engaging in lending and liquidation under the influence of severe price discrepancies to obtain unexpected profits. The SlowMist security team recommends that project parties enhance the anti-manipulation capabilities of price oracles and design a more secure oracle feeding mechanism to prevent similar incidents from occurring again.
