GalloDaSballo - PreviewRedeem may under-price the value of the asset

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GalloDaSballo

medium

PreviewRedeem may under-price the value of the asset

Summary

previewRedeem will return an incorrect result based on address(0)

If you get the partnership the fee changes, the address could change the value
This may enable: Unfairer (bps wise), liquidations when they shouldn't happen, also will enable marginally higher profit for liquidators as they may be able to benefit from the reduction of the fee

Vulnerability Detail

Impact

A user may get liquidated earlier, and the accounting would be incorrect

Code Snippet

https://arbiscan.io/address/0x13f0d29b5b83654a200e4540066713d50547606e#code

  function previewRedeem(address _addr, uint256 _shares)
    external
    view
    returns (
      uint256 _exitFeeLessRebate,
      uint256 _rebateAmount,
      uint256 _assetsLessFee
    )
  {
    PartnerInfo memory partner = partners[_addr];
    uint256 exitFee = partner.isActive ? partner.exitFee : defaultExitFee;
    uint256 rebate = partner.isActive ? partner.rebate : defaultVaultRebate;
    uint256 assets = IERC4626(vault).previewRedeem(_shares);

    uint256 _exitFee;
    (_exitFee, _assetsLessFee) = _calculateFee(assets, exitFee);
    (_rebateAmount, _exitFeeLessRebate) = _calculateFee(_exitFee, rebate);
  }

Tool used

Manual Review

Recommendation

Use the account to determine the price