# Withdrawals of rebasing tokens can lead to insolvency and unfair distribution of protocol reserves

WithdrawQueue stores fixed stETH amounts instead of shares, so rebasing lets early claimers dodge losses, DoSing later claims and leaving ezETH uncollateralized.

- Payout: Contest reward
- Severity: high
- Program: Renzo
- Credited: LessDupes
- Disclosed: 2024-06-07
- Write-up quality: 7/10
- Original: https://github.com/code-423n4/2024-04-renzo-findings/issues/282
- Library page: https://bugbountylibrary.com/r/c4%3A2024-04-renzo%3AH-05
- Tags: domain:web3 impact:dos impact:funds-loss impact:integrity kind:contest platform:code4rena sev:high tech:evm tech:solidity technique:source-review vuln:business-logic vuln:oracle-manipulation

**Target:** WithdrawQueue.sol withdrawal/claim flow for rebasing LSDs
**Root cause:** withdraw() records a fixed amountToRedeem in stETH units rather than stETH shares; rebasing changes the contract's stETH balance while stored amounts stay fixed, so claims no longer match reserves.
**Steps:**
1. Alice and Bob deposit stETH, receive ezETH (90/10).
2. Bob calls `withdrawQueue.withdraw(10e18, stETH)`; Alice calls `withdraw(90e18-1, stETH)`.
3. Simulate negative rebase: transfer 10e18 stETH out of WithdrawQueue.
4. Warp 10 days; Alice calls `claim(0)` and receives full 90e18-1 stETH.
5. Bob calls `claim(0)` and reverts on insufficient balance; TVL drops to ~1 wei while ezETH supply unchanged.
**How found:** Code review of withdraw()/claim() noticed amountToRedeem stored as a fixed token amount and transferred via IERC20.transfer, ignoring that stETH is rebasing (share-based); reasoned through slashing scenario comparing rebasing vs non-rebasing LSDs.
**Exploitation:** A withdrawing user front-runs a negative rebase by having their fixed stETH amount recorded pre-rebase, then claims the full pre-rebase amount after the balance shrinks, shifting the loss onto remaining users and the protocol; later claimers revert.
**Escalation:** Loss concentrates on last exiters; protocol TVL collapses while ezETH supply stays constant, rendering ezETH uncollateralized.
**Insight:** When a protocol custodies rebasing/share-based tokens (stETH, aTokens), check whether accounting stores token amounts or shares; any stored fixed amount diverges from actual balance on rebase, letting early exiters dodge losses.