First Flight #18: T-Swap
First Flight #18
Beginner FriendlyDeFiFoundry
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Submission Details
Severity: high
Valid

`TSwapPool::sellPoolTokens` mismatches input and output tokens and users receive the incorrect amount of tokens

maikelordaz

TSwapPool::sellPoolTokens mismatches input and output tokens and users receive the incorrect amount of tokens

Description: The sellPoolTokens function is intended to allow users to easily sell pool tokens and receive WETH in exchange. Users indicate how many pool tokens they're willing to sell in the poolTokenAmount parameter. However, the function does a wrong calculation in the swapped amount.

This is due to the fact that the swapExactOutput function is called, instead the swapExactInput function.

Impact: Users will swap the wrong amount of tokens, which is a severe disruption of protcol functionality.

Recommended Mitigation:

Consider changing the implementation to use swapExactInput instead of swapExactOutput. Note that this would also require changing the sellPoolTokens function to accept a new parameter (ie minWethToReceive to be passed to swapExactInput)

function sellPoolTokens(
uint256 poolTokenAmount,
+ uint256 minWethToReceive,
) external returns (uint256 wethAmount) {
- return swapExactOutput(i_poolToken, i_wethToken, poolTokenAmount, uint64(block.timestamp));
+ return swapExactInput(i_poolToken, poolTokenAmount, i_wethToken, minWethToReceive, uint64(block.timestamp));
}
Updates

Appeal created

inallhonesty Lead Judge about 1 year ago
Submission Judgement Published
Validated
Assigned finding tags:

`sellPoolTokens` mismatches input and output tokens causing users to receive the incorrect amount of tokens

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