Lines of code
<https://github.com/pooltogether/v4-twab-delegator/blob/2b6d42506187dd7096043e2dfec65fa06ab18577/contracts/PermitAndMulticall.sol#L31-L37&gt;
<https://github.com/pooltogether/v4-twab-delegator/blob/2b6d42506187dd7096043e2dfec65fa06ab18577/contracts/TWABDelegator.sol#L438-L445&gt;

Vulnerability details

Impact

When the _from address is not the msg.sender _multiCall() will be made on behalf of the msg.sender. As a result each of the functions called by multiCall() will be made on behalf of msg.sender and not _from.

If functions such as transfer() or unstake() are called msg.sender will be the original caller which would transfer the attacker the funds if the to field is set to an attackers address.

Furthermore, if an attacker we to call permitAndMulticall() before the _from user they may use their signature and nonce combination. As a nonce is only allowe to be used once the siganture will no longer be valid and _permitToken.permit() will fail on the second call.

An attacker may use this as a Denial of Service (DoS) attack by continually front-running permitAndCall() using other users signatures.

Proof of Concept

  function _multicall(bytes[] calldata _data) internal virtual returns (bytes[] memory results) {
    results = new bytes[](_data.length);
    for (uint256 i = 0; i < _data.length; i++) {
      results[i] = Address.functionDelegateCall(address(this), _data[i]);
    }
    return results;
  }



  function _permitAndMulticall(
    IERC20Permit _permitToken,
    address _from,
    uint256 _amount,
    Signature calldata _permitSignature,
    bytes[] calldata _data
  ) internal {
    _permitToken.permit(
      _from,
      address(this),
      _amount,
      _permitSignature.deadline,
      _permitSignature.v,
      _permitSignature.r,
      _permitSignature.s
    );

    _multicall(_data);
  }

Recommended Mitigation Steps

Consider updating the _from field to be the msg.sender in permitAndMulticall() (or alternatively do this in _permitAndMulticall() to save some gas).

  function permitAndMulticall(
    uint256 _amount,
    Signature calldata _permitSignature,
    bytes[] calldata _data
  ) external {
    _permitAndMulticall(IERC20Permit(address(ticket)), msg.sender, _amount, _permitSignature, _data);
  }

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