58322 sc low incorrect emit due to wrong ordering of wethbalancebefore calculation

Submitted on Nov 1st 2025 at 09:08:33 UTC by @SOPROBRO for Audit Comp | Alchemix V3

• Report ID: #58322

• Report Type: Smart Contract

• Report severity: Low

• Target: https://github.com/alchemix-finance/v3-poc/blob/immunefi_audit/src/strategies/mainnet/MorphoYearnOGWETH.sol

• Impacts:

  • Contract fails to deliver promised returns, but doesn't lose value

Description

Brief/Intro

In MorphoYearnOGWETH::_deallocate, the function incorrectly calculates wethBalanceBefore after performing the vault.withdraw call. This causes wethRedeemed to always evaluate to 0, resulting in an incorrect emission of a StrategyDeallocationLoss event even when there is no actual loss.

Vulnerability Details

vault.withdraw(amount, address(this), address(this));
// @audit `wethBalanceBefore` is calculated after withdrawal
uint256 wethBalanceBefore = TokenUtils.safeBalanceOf(address(weth), address(this));
uint256 wethBalanceAfter = TokenUtils.safeBalanceOf(address(weth), address(this));
uint256 wethRedeemed = wethBalanceAfter - wethBalanceBefore;
if (wethRedeemed < amount) {
	emit StrategyDeallocationLoss("Strategy deallocation loss.", amount, wethRedeemed);
}

The issue is that wethBalanceBefore should represent the contract’s WETH balance before the withdrawal is executed. However, since it is calculated after the vault.withdraw call, both wethBalanceBefore and wethBalanceAfter are the same, leading to:

wethRedeemed = wethBalanceAfter - wethBalanceBefore = 0

This triggers a false StrategyDeallocationLoss event regardless of whether the strategy incurred a real loss.

Impact Details

The StrategyDeallocationLoss event will always be emitted, even when there are no losses, which may result in false alerts

References

(Code Location) https://github.com/alchemix-finance/v3-poc/blob/a192ab313c81ba3ab621d9ca1ee000110fbdd1e9/src/strategies/mainnet/MorphoYearnOGWETH.sol#L50-L56

Proof of Concept

Proof Of Concept

Add the following test to MorphoYearnOGWETHStrategy.t.sol and run in the console forge test --mt test_strat_always_emits_strat_loss -vv, and see that the following event will be emitted emit StrategyDeallocationLoss("Strategy deallocation loss.", 5e18, 0);

event StrategyDeallocationLoss(string message, uint256 amountRequested, uint256 actualAmountSent);

function test_strat_always_emits_strat_loss() public {
	uint256 amountToAllocate = 10e18;
	uint256 amountToDeallocate = amountToAllocate / 2;
	vm.startPrank(vault);
	deal(testConfig.vaultAsset, strategy, amountToAllocate);
	bytes memory prevAllocationAmount = abi.encode(0);
	IMYTStrategy(strategy).allocate(prevAllocationAmount, amountToAllocate, "", address(vault));
	bytes memory prevAllocationAmount2 = abi.encode(amountToAllocate);
	vm.expectEmit();
	emit StrategyDeallocationLoss("Strategy deallocation loss.", 5e18, 0);
	IMYTStrategy(strategy).deallocate(prevAllocationAmount2, amountToDeallocate, "", address(vault));
}