Submitted by kenzo, also found by 0x29A, cccz, csanuragjain, GimelSec, kirk-baird, Lambda, sashiketh, shenwilly, and StErMi_
ERC5095s redeem/withdraw allows an ERC20-approved account to redeem users tokens, but does not update the allowance after burning.
User Mal can burn more tokens than Alice allowed him to.
He can set himself to be the receiver of the underlying, therefore Alice will lose funds.
withdraw and redeem functions check that the msg.sender has enough approvals to redeem the tokens:
But they do not update the allowances.
They then call authRedeem, which also does not update the allowances.
Therefore, an approved user could re-use his approval again and again and redeem whole of approvers funds to himself.
Update the allowances upon spending.
sourabhmarathe (Illuminate) confirmed and commented:
