DittoETH
Ditto
DeFiFoundryOracle
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Submission Details
Severity: low
Valid

zETH minting is vulnerable to any attack or price fluctuation in stETH protocol.

836541

Summary

In BridgeRouterFacet.sol, both deposit and depositEth methods deposit the user's collateral via bridge, and the bridge returns a zETH amount which the BridgeRouterFacet.sol should credit to the user. However, while for rETH bridge the bridge uses a oracle to convert rETH to ETH to return a precise amount of zETH, the stETH bridge just returns the value of stETH the user deposited, assuming that stETH:ETH:zETH, which makes the protocol vulnerable to exploits and price fluctuations of stETH.

Vulnerability Details

  1. In BridgeRouterFacet.sol, both deposit and depositETH has this line of code:

uint88 zethAmount = uint88(IBridge(bridge).deposit(msg.sender, amount));

It returns a value of zethAmount which uses should get based on how much he deposited.

  1. When user deposits stETH, the method depositEth in BridgeSteth.sol is called:

function depositEth() external payable onlyDiamond returns (uint256) {
uint256 originalBalance = steth.balanceOf(address(this));
// @edv address(0) means no fee taken by the referring protocol
steth.submit{value: msg.value}(address(0));
uint256 netBalance = steth.balanceOf(address(this)) - originalBalance;
if (netBalance == 0) revert NetBalanceZero();
return netBalance;
}

  1. The method above just retuns the netBalance, which is the value of stETH you deposited as the zETHAmount. This is flawed, because any attack or price fluctuation in stETH that decreases it's value will directly impact our bridge. For example, if stETH is 90% of ETH price, then users are getting zETH in our protocol with 10% discount.

Impact

Probability: Low.
Severity: High.
Impact: Medium.

The security of "minting" zETH via stETH deposits have a great dependancy in stETH price.

Tools Used

Manual Review

Recommendations

To avoid this, the stETH:ETH chainlink oracle should be used.

Updates

Lead Judging Commences

0xnevi Lead Judge about 2 years ago
Submission Judgement Published
Validated
Assigned finding tags:

finding-579

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